Chilton's General Motors Chevy/GMC Pick-Ups & Suburban 1980-1987 Repair Manual 0801985773, 9780801985775

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Chevy /GMC 1/2, 3/4, 1Ton Pick-up, Blazer, Jimmy and Suburbans 2

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and 4-wheel oldM(Do not attempt to test the crankcase controls on these diesels. Instead, clean the valve cover filter assembly and vent pipes and check the vent pipes. Replace the breather cap assembly every 30,000 miles. Replace all rubber fittings as required every 15,000 miles.

85771089

Fig. 21 To free the crankcase breather, remove the C-

clip from breather neck on the outside of the air cleaner assembly

10 SERIES

20 SERIES 85771017

Fig. 22 PCV locations. Inline six valve also in valve cover

1-14

ROUTINE MAINTENANCE

VENTILATION FILTER

SEPRESSION

REGULATOR

pa INLET PORT (2) (GASES FROM CRANKCASE)

MOUNTING

,

bas! BREATHER VENTILATION

COVER Ar DIAPHRAGM

OUTLET TUBE (GASES TO

CAP

INTAKE MANIFOLD)

FILTER

DIESEL CRANKCASE VENTILATION SYSTEM

CRANKCASE

DEPRESSION

REGULATOR 85771019

Fig. 23 Diesel crankcase ventilation flow and depression regulator

Evaporative Canister » See Figure 24

SERVICING The only regular maintenance that need be performed on the evaporative emission canister is to regularly change the filter and check the condition of the hoses. If any hoses need replacement, use only hoses which are marked EVAP. No other types should be used. Whenever the vapor vent hose is replaced, the restrictor adjacent to the canister should also be replaced. The evaporative emission canister is located on the left side of the engine compartment, with a filter located in its bottom. The filter should be replaced according to the scheduled maintenance. To service the canister filter: 1. Note the installed positions of the hoses, tagging them as necessary, in case any have to be removed. 2. Loosen the clamps and remove the bottom of the canister. 3. Pull the filter out and throw it away. 4. Install a new canister filter. 5. Install the bottom of the canister and tighten the clamps. 6. Check the hoses for cracks, restrictions or hose connection openings. 85771018

Fig. 24 Example of GM evaporative canister

ROUTINE MAINTENANCE Battery » See Figures 26, 27, 28, 29, 30, 31 and 35

GENERAL MAINTENANCE Check the battery fluid level (except in Maintenance Free batteries) at least once a month, more often in hot weather or during extended periods of travel. The electrolyte level should be up to the bottom of the split ring in each cell. All batteries

on Chevrolet and GMC trucks are equipped with an eye in the cap of one cell. If the eye glows or has an amber color to it, this means that the level is low and only distilled water should be added. Do not add anything else to the battery. If the eye has a dark appearance the battery electrolyte level is high enough. It is wise to also check each cell individually. At least once a year, clean and tighten the battery cable clamps and apply a thin coat of petroleum jelly to the terminals. This will help to retard corrosion. The terminals can be

1-15

Battery State of Charge at Room Temperature Specific Gravity Reading

Charged Condition

Fully Charged ¥_ Charged V2 Charged

1.260—1.280 1.230—1.250 1.200—1.220 1.170—1.190 1.140—1.160 1.110—1.130

VY, Charged Almost no Charge No Charge 85771026

Fig. 25 Battery state of charge

RING BOTTOM

cleaned with a stiff wire brush or with an inexpensive terminal cleaner designed for this purpose.

lf water is added during freezing weather, the truck should be driven several miles to allow the electrolyte and water to mix. Otherwise the battery could freeze. lf the battery becomes corroded, a solution of baking soda and water will neutralize the corrosion. This should be washed off after making sure that the caps are securely in place. Rinse the solution off with cold water. Some batteries were equipped with a felt terminal washer. This washer should be saturated with engine oil every 6,000 miles. Doing so will help to retard corrosion. lf a fast charger is used while the battery is in the truck, disconnect the battery before connecting the charger.

85771020

Fig. 26 Fill each battery cell to the bottom of the split ring with distilled water

°K CAUTION Keep flame or sparks away from the battery; it gives off explosive hydrogen gas.

Fig. 27 The specific gravity of the battery can be checked with a simple float-type hydrometer

85771022

Fig. 28 Special pullers are available to remove cable clamps

1-16

ROUTINE MAINTENANCE

85771023

Fig. 29 Clean the battery posts with a wire brush, or the special tool shown

level checks are concerned. However, the terminals require periodic cleaning, which should be performed at least once a ear. d The sealed top battery cannot be checked for charge in the normal manner, since there is no provision for access to the marine To check the condition of the battery: If the indicator eye on top of the battery is dark, the ee has enough fluid. If the eye is light, the electrolyte fluid is too low and the battery must be replaced. 2. If a green dot appears in the middle of the eye, the battery is sufficiently charged. Proceed to Step 4. If no green dot is visible, charge the battery as in Step 3. 3. Charge the battery at the rate specified below.

Charging Rate Amps 75 50 25 10 85771027

85771

Fig. 30 Clean the inside of the cable clamp with a wire brush

Fig. 32 Battery charging rate

i CAUTION Do not charge the battery for more than 50 amp/hours. If the green dot appears, or if electrolyte squirts out of the vent hole, stop the charge and proceed to Step 4.

85771025

Fig. 31 Special tools are available for cleaning the terminals and cable clamps on side terminals batteries

TESTING Maintenance Free Battery All later model trucks are equipped with maintenance free batteries, which do not require normal attention as far as fluid

4. It may be necessary to tip the battery from side to side to get the green dot to appear after charging. 5. Disconnect the battery cables from the battery. Connect a battery load tester and a voltmeter across the battery terminals. Apply a 300 amp load to the battery for 15 seconds to remove the surface charge. Do not leave the load on the battery for longer that 15 seconds. 6. Wait 15 seconds to allow the battery to recover. 7. Apply the test load, as specified in the appropriate chart. Only apply the load on the battery for 15 seconds while reading the voltage. Once the voltage is recorded, discontinue the battery load. 8. Check the results against the desired readings in the proper chart. If the battery voltage is at or above the specified voltage for the temperature listed, the battery is good. If the battery is good be sure to test the battery cables. If the voltage falls below what’s listed, the battery should be replaced.

ROUTINE MAINTENANCE a

SSS

SSS

1-17

SSS

make sure that the replacement cable is routed in exactly the same way that the original was. —_eV_—_e——————————————

Test Load 130 170 210 230

amps amps amps amps 85771028

Fig. 33 Battery load specifications

Battery Cable Testing 1. Fully charge the battery. 2. To prevent the vehicle from starting during the test, perform the following: a. On vehicles equipped with HEI electronic ignition, disconnect the wire harness connectors at the HEI distributor. Do not disconnect the spark plug wires. b. On vehicles equipped with a conventional point type ignition, disconnect the ignition primary wire at the distributor cap and ground it using a jumper. 3. Connect a voltmeter’s test leads to each end of the positive battery cable with the battery cable still connected.

«CAUTION Temperature

Minimum

(CF)

Voltage

70 or above

Be sure that all hands, clothing, test leads and voltmeter

are clear of any moving parts such as the fan, belts or pulleys before proceeding.

9.6 SHS) 9.4 9.3 9.1 8.9

8.7 8.5 85771029

Fig. 34 Battery voltage specifications Non-Maintenance Free Battery 1. Connect a voltmeter and battery load tester to the battery terminals. 2. Apply a 300-ampere load for 15 seconds to remove surface charge from the battery. Remove the load. 3. Wait 15 seconds to allow the battery to recover. Then apply the load specified on the battery’s label. After 15 seconds, read the voltage and remove the load. 4. If the voltage does not drop below 9.5 volts, the battery can be judged as good. 5. If the voltage is less than 9.5 volts, you can try to charge it, but replacement is recommended.

BATTERY CABLES Battery cables have a tendency to corrode from the inside out. When this occurs, electrical resistance builds up in the cable resulting in a voltage drop across the cable. If the voltage drop is high enough a no start or a slow cranking condition will occur. Since this condition eventually causes the battery to go dead gradually, many people have mistakenly replaced batteries and alternators that were not really bad. The battery cables should be checked whenever hard starting is noticed, a jump is required or a large amount of corrosion is observed at the battery terminals. Whenever you replace a battery cable, be sure to use a replacement cable that is the same gauge and length. Be sure

to replace all additional feed wires and/or ground leads. Also,

4. Observe the voltmeter while having an assistant crank the engine. If the voltmeter reads 0.5 volts or higher, replace the cable. 5. Repeat Steps 3 and 4 to test the negative battery cable, but connect the voltmeter across the two ends of the negative battery cable. : 6. Reconnect the distributor after you have checked both cables.

CHARGING If charging the battery while it is installed in the vehicle, be sure the ignition switch is OFF. Failing to do so may damage on board computers and other electrical components. It is best to remove the battery and charge it slowly with a trickle charger, following the instructions provided with the charger. Some important points to remember when charging a battery: e Use the proper adaptors for the side-terminal battery found on your truck. e Do not attempt to charge a battery with clear or light yellow hydrometer eye on the battery. e Do not attempt to charge a frozen battery. e Charge the battery at room temperature. e During the charge, monitor the battery at least hourly. Discontinue the process if the battery temperature exceeds 125°F (52°C) or if any fluid or visible gas is spewing from the vapor holes. e Charge until the green dot appears, then load test it to ensure a full charge.

REPLACEMENT When choosing a replacement battery, it is important to adhere to the original equipment specifications. If your vehicle is a base version, the Cold-Cranking Amperage (CCA) and the Reserve Capacity Rating should be no less than the original equipment battery. If your truck is equipped with electric op-

1-18

ROUTINE MAINTENANCE

tions, the Cold-Cranking Amperage (CCA) should be no less than 770 and the Reserve Capacity Rating should be no less than 115. 1, Make sure the ignition is off. Disconnect the negative battery cable, then the positive cable. 2. Remove the battery hold-down bolt and retainer. ’ 3. Remove the battery from the battery tray. 4. Install the battery and all removed parts. 5. Connect the positive battery cable, then the negative battery cable.

JUMP STARTING Except Diesels The following procedure is recommended by the manufacturer. Be sure that the booster battery is 12 volt with negative ground.

CAUTION Do not attempt this procedure on a frozen battery; it may explode. Do not attempt it on a sealed Delco Freedom battery showing a light color in the charge indicator. Be certain to observe correct polarity connections. Failure to do so will result in almost immediate alternator and regulator destruction. Never allow the jumper cable ends to touch each other. 1. Position the vehicles so that they are not touching. Set the parking brake and place automatic transmissions in Park

and manual transmissions in Neutral. Turn off the lights, heater

and other electrical loads. 2. Remove the vent caps from both the booster and discharged battery. Lay a cloth over the open vent cells of each battery. This isn’t necessary on batteries equipped with sponge type flame arrestor caps, and it isn’t possible on sealed batteries. 3. If the terminals on the run-down battery are heavily corroded, clean them before connecting the jumper cables 4. Identify the negative and positive terminals on both batteries. Connect the jumper cables in the following order: a. First, connect the jumper cable to the dead battery’s positive terminal. b. Second, connect the other end of this cable to the good battery’s positive terminal. c. Third, connect the second jumper cable to the good battery’s negative terminal. d. The last connection with the second jumper cable should be made to a good ground on the dead vehicle, such as the engine block but as far away from the battery as possible. e, Check that the jumper cables are clear of all moving parts such as the fan, fan belts or pulleys etc. 5. Start the engine of the working vehicle and run it at fast idle. Try to start the vehicle with the dead battery. Crank it for no more than 10 seconds at a time and let it cool off for 20 seconds in between tries. 6. If the vehicle does not start in 3 attempts, there is something else wrong. 7. Disconnect the jumper cables in the reverse order. 8. Replace the cell covers and dispose of the rags. Diesels

JUMP-STARTING A DUAL BATTERY DIESEL

All GM V8 diesels are equipped with two 12 volt batteries. The batteries are connected in parallel circuit, positive terminal to positive terminal and negative terminal to negative terminal. Hooking the batteries up in parallel circuit increases battery cranking power without increasing total battery voltage output (12 volts). On the other hand, hooking two 12 volt batteries up in a series circuit (positive terminal to negative terminal, positive terminal to negative terminal) increases total battery output to 24 volts (12 volts + 12 volts).

i

CAUTION

ae

NEVER hook the batteries up in a series circuit or the entire electrical system will be damaged.

85771090

Fig. 35 When loosening or tightening the battery cable from the positive terminal, take extra care not to allow the wrench to touch/ground on any metal surface

In the event that a dual battery diesel must be jump started, use the following procedure: 1. Open the hood and locate the batteries. On GM diesels, the manufacturer usually suggests using the battery on the driver's side of the car to make the connection. 2. Position the vehicle so that the jumper cables will reach from its battery (must be 12 volt, negative ground) to the ages battery in the diesel. Do not allow the vehicles to ouch. 3. Shut off all electrical equipment on both vehicles. Turn off the engine of the vehicle with the good battery, set the parking brakes on both vehicles and block the wheels. Also,

ROUTINE MAINTENANCE

1-19

make sure both vehicles are in Neutral (manual transmission models) or Park (automatic transmission models). 4. Using the jumper cables, connect the positive (+) terminal of the good battery to the positive terminal of one (not both) of the diesel batteries. 5. Using the second jumper cable, connect the negative (-) terminal of the good battery to a solid, stationary, metallic point on the diesel (alternator bracket, engine block, etc.) Be very careful to keep the jumper cables away from moving parts (cooling fan, alternator belt, etc.) on both vehicles. 6. Start the engine on the vehicle with the good battery and run it at moderate speed.

7. Start the engine of the diesel. 8. When the diesel starts, disconnect the battery cables in the reverse order of attachment.

SERVICING » See Figure 36 The heat riser is a thermostatically or vacuum operated valve in the exhaust manifold. Not all engines have one. Heat riser equipped V8s have only one valve, located in the right manifold. The valve opens when the engine is warming up, to direct hot exhaust gases to the intake manifold, in order to preheat the incoming fuel/air mixture. If it sticks shut, the result will be frequent stalling during warm-up, especially in cold and damp weather. If it sticks open, the result will be a rough idle after the engine is warm. The heat riser should move freely. If it sticks, apply GM Manifold Heat Control Solvent or something similar (engine cool) to the ends of the shaft. Sometimes rapping the end of the shaft sharply with a hammer (engine hot) will break it loose. If this fails, components must be removed for further repairs.

Drive Belts

INSPECTION At the interval specified in the Maintenance Intervals chart, check the water pump, alternator, power steering pump (if equipped), air conditioning compressor (if equipped) and air pump (if equipped) drive belts for proper tension. Also look for signs of wear, fraying, separation, glazing, and so on, and replace the belts as required.

OG)

[2] [3] [4] [5]

EXHAUST MANIFOLD

VACUUM SOURCE HOSE EFE ACTUATOR EXHAUST PIPE

4S 05516E 85771030

Fig. 36 Vacuum heat riser valve than 12 inches, deflection can range between ‘se inch and % inch.

REMOVAL & INSTALLATION » See Figures 41, 42, 43 and 44 1. Loosen the driven accessory’s pivot and mounting bolts. 2. Move the accessory toward the engine until enough slack is created to remove the belt from the pulley. To install: 3. Place the new belt over the pulley and move the accessory away from the engine until the tension is correct. You can use a wooden hammer handle, or broomstick, as a lever, but do not use anything metallic, such as a prybar.

ADJUSTMENT » See Figures 37, 38, 39 and 40 Belt tension should be checked with a gauge made for the purpose, while the engine is OFF. If a tension gauge is not available, tension can be checked with moderate thumb pres-

sure applied to the belt at its longest span midway between pulleys. If the belt has a free span less than 12 inches, it should deflect approximately ‘/s-'/s inch. If the span is longer

7 TO 10” 1/4" DEFLECTION

|+_—- 13" TO 16" eel 1/2" DEFLECTION 85771031

Fig. 37 A gauge is recommended, but you can check belt tension with thumb pressure

1-20

ROUTINE MAINTENANCE

85771 85771091

Fig. 38 To adjust a drive belt’s tension, loosen the mounting and adjusting bolts in order to allow the component to pivot

Fig. 40 prytool proper to hold

To tighten the belt on this alternator, a wooden was inserted behind the housing. Once the tension is reached, the adjuster bolt is tightened the component in place

85771032

Fig. 41 Push the component toward the engine and slip off the belt

4. Tighten the bolts and recheck the tension. If new belts have been installed, run the engine for a few minutes. With the engine OFF, recheck and readjust the belt as necessary. It is better to have belts too loose than too tight, because overly tight belts will lead to bearing failure, particularly in the water pump and alternator. However, loose belts place an extremely high impact load on the driven component due to the whipping action of the belt.

85771092

Fig. 39 Some components and brackets, such as the AIR pump, contain square fittings in which a ratchet may be inserted and used to pivot the component

Upper and lower radiator hoses and all heater hoses should be checked for deterioration, leaks and loose hose clamps every 15,000 miles.

ROUTINE MAINTENANCE — 1-21 REMOVAL & INSTALLATION 1. Drain the radiator as detailed later in this Section.

KCAUTION

85771033 Fig. 42 Slip the new belt over the pulley

|

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 2. Loosen removed. 3. Working tion and then 4. Position the hose and

the hose clamps at each end of the hose to be the hose back and forth, slide it off its connecinstall a new hose if necessary. the hose clamps at least ‘/; in. from the end of tighten them.

e» Always make sure that the hose clamps are beyond the bead and place in the center of the clamping surface before tightening them. 85771034

Fig. 43 Pull outward on the component and tighten the mounting bolts

ENGINE

ADJUSTING

ADJUSTING BOLT

: BRACE-A/CL

GENERATOR

AIR CONDITIONING 85771035

ig. 44 379 Diesel belt adjustments

ae be

1-22

ROUTINE MAINTENANCE

Air Conditioning SAFETY WARNINGS R-12 refrigerant is a chlorofluorocarbon which, when re-

leased into our atmosphere, contributes to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun. Be sure to consult laws in your area before servicing the air conditioning system. In some areas, it is illegal for an unlicensed individual to perform repairs involving refrigerant. Because of the importance of the necessary safety precautions that must be exercised when working with air conditioning systems and R-12 refrigerant, a recap of the safety precautions is outlined. 1. Avoid contact with a charged refrigeration system, even when working on another part of the air conditioning system or vehicle. If a heavy tool comes into contact with a section of copper tubing or a heat exchanger, it can easily cause the relatively soft material to rupture. 2. When it is necessary to apply force to a fitting which contains refrigerant, as when checking that all system couplings are securely tightened, use a wrench on both parts of the fitting involved, if possible. This will avoid putting torque on the refrigerant tubing. It is advisable, to use tube or line wrenches when tightening these flare nut fittings. 3. Do not attempt to discharge the system refrigerant to the atmosphere by merely loosening a fitting, or removing the service valve caps and cracking these valves. Precise control and proper containment is possible only when using the service gauges and a recovery station. Wear protective gloves when connecting or disconnecting service gauge hoses. 4. Never start a system without first verifying that both service valves are backseated, if equipped, and that all fittings throughout the system are snugly connected. 5. Avoid applying heat to any refrigerant line or storage vessel. Charging may be aided by using water heated to less than 125°F (52°C) to warm the refrigerant container. Never allow a refrigerant storage container to sit out in the sun, or near any other source of heat, such as a radiator.

6. Always wear safety goggles when working on a system to protect the eyes. If refrigerant contacts the eye, it is advisable in all cases to see a physician as soon as possible. 7. Frostbite from liquid refrigerant should be treated by first gradually warming the area with cool water, and then gently applying petroleum jelly. A physician should be consulted. 8. Always keep refrigerant container fittings capped when not in use. Avoid sudden shock to the refrigerant container which might occur from dropping it, or from banging a heavy tool against it. Never carry a refrigerant can in the passenger compartment of a car. 9. Always completely discharge the system before painting the vehicle if the paint is to be baked on, or before welding anywhere near the refrigerant lines.

GENERAL INFORMATION The most important aspect of air conditioning service is the maintenance of pure and adequate charge of refrigerant in the system. A refrigeration system cannot function properly if a significant percentage of the charge is lost. Leaks are common because the severe vibration encountered in an automobile can easily cause a sufficient cracking or loosening of the air conditioning fittings. As a result, the extreme operating pressures of the system force refrigerant out. The problem can be understood by considering what happens to the system as it is operated with a continuous leak. Because the orifice tube regulates the flow of refrigerant to the evaporator, the level of refrigerant there is fairly constant. The accumulator-drier stores any excess of refrigerant, and so a loss will first appear there as a reduction in the level of liquid. As this level nears the bottom of the vessel, some refrigerant vapor bubbles will begin to appear in the stream of liquid supplied to the orifice tube. This vapor decreases the capacity of the orifice tube very little as the valve opens to compensate for its presence. As the quantity of liquid in the condenser decreases, the operating pressure will drop there and throughout the high side of the system. As the R-12 continues to be expelled, the pressure available to force the liquid through the orifice tube will continue to decrease, and, eventually, the orifice will prove to be too much of a restriction for adequate flow. At this point, low side pressure will start to drop, and severe reduction in cooling capacity, marked by freeze-up of the evaporator coil, will result. Eventually, the operating pressure of the evaporator will be lower than the pressure of the atmosphere surrounding it, and air will be drawn into the system wherever there are leaks in the low side. Because all atmospheric air contains at least some moisture,

water will enter the system and mix with the R-12 and the oil. Trace amounts of moisture will cause sludging of the oil, and corrosion of the system. Saturation and clogging of the accumulator-drier, and freezing of the orifice will eventually result. As air fills the system to a greater and greater extent, it will interfere more and more with the normal flows of refrigerant and heat. A list of general precautions that should be observed while

doing this follows:

1. Keep all tools as clean and dry as possible. 2. Thoroughly purge the service gauges and hoses of air and moisture before connecting them to the system. Keep them capped when not in use. 3. Thoroughly clean any refrigerant fitting before disconnecting it, in order to minimize the entrance of dirt into the system.

4. Plan any operation that requires opening the system beforehand in order to minimize the length of time it will be exposed to open air. Cap or seal the open endsto minimize the entrance of foreign material. 5. When adding oil, pour it through an extremely clean and dry tube or funnel. Keep the oil capped whenever possible. Do not use oil that has not been kept tightly sealed. 6. Use only Refrigerant 12 (R-12). Purchase refrigerant intended for use in only automotive air conditioning system. Avoid the use of R-12 that may be packaged for another use, such as cleaning, or powering a horn, as it is impure.

ROUTINE MAINTENANCE — 1-23 7. Completely evacuate any system that has been opened to replace a component, other than when isolating the compressor, or that has leaked sufficiently to draw in moisture and air. This requires evacuating air and moisture with a good vacuum pump for at least one hour. If a system has been open for a considerable length of time it may be advisable to evacuate the system for up to 12 hours (overnight). 8. Use a wrench on both halves of a fitting that is to be disconnected, so as to avoid placing torque on any of the refrigerant lines.

ACCUMULATOR OUTLET

EVAPORATOR INLET

SYSTEM INSPECTION » See Figure 45

CAUTION Do not attempt to charge or discharge the refrigerant system unless you are thoroughly familiar with its operation and the hazards involved. The compressed refrigerant used in the air conditioning system expands and evaporates (boils) into the atmosphere at a temperature of -21.7°F (-29.8°C) or less. This will freeze any surface that it comes in contact with, including your eyes. In addition, the refrigerant decomposes into a poisonous gas in the presence of flame. Before proceeding with the Temperature Test, the following checks should be made since these items can also degrade air conditioning system performance: 1. Check the antifreeze protection. In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain permanent type antifreeze protection of +15°F (9°C) or lower. A reading of +15°F (26°C) is ideal since this protection also supplies sufficient corrosion inhibitors for the protection of the engine cooling system. 2. Check the radiator cap. For efficient operation of an air conditioned car’s cooling system, the radiator cap should have a holding pressure which meets manufacturer's specifications. A cap which fails to hold these pressure should be replaced. 3. Check the condenser for any obstructions or damage. Any obstructions will restrict the air flow which is essential to the system’s efficient operation. 4. Check that the condenser drain tube expels the condensation, which accumulates on the bottom of the evaporator housing, into the engine compartment. If this tube is obstructed, the air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle’s floor.

85771038

Fig. 45 Checking evaporator inlet and accumulator outlet line temperature

DISCHARGING THE SYSTEM » See Figures 46 and 47 e*R-12 refrigerant is a chlorofluorocarbon which, when re-

leased into the atmosphere, can contribute to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun. An approved R-12 Recovery/Recycling machine that meets SAE standards should be used when discharging the system. Follow the operating instructions provided with the equipment exactly to properly discharge the system. 1. Remove the caps from the high and low pressure charging valves in the high and low pressure lines. 2. Connect an approved R-12 Recovery/Recycling machine to the valves and follow the instructions provided with the unit. 3. Open the low pressure gauge valve slightly and allow the system pressure to bleed off. 4. When the system is just about empty, open the high pressure valve very slowly to avoid losing an excessive amount of refrigerant oil. Do not allow any refrigerant to escape.

EVACUATING THE SYSTEM 1. Discharge the system. 2. Connect the proper service hose to the inlet fitting of the vacuum pump. 3. Turn both gauge valves to the wide open position. 4. Start the pump and note the low side gauge reading.

Temperature Test

1. Warm the engine to normal operating temperature. 2. Open the hood and doors. 3. Set the sélector lever at A/C. 4. Set the temperature lever at the first detent to the right of COLD (outside air). 5. Set the blower on HI. 6. Idle the engine at 1,000 rpm.

7. Feel the temperature of the evaporator inlet and the accumulator outlet with the compressor engaged. Both lines should be cold. If the inlet pipe is colder than the outlet pipe the system is low on charge.

4

Fig. 46 High pressure line valve located between the compressor and the condenser

1-24

ROUTINE MAINTENANCE turned off. If the needle drops to zero rapidly, there is a leak in the system which must be repaired.

CHARGING THE SYSTEM

«CAUTION NEVER OPEN THE HIGH PRESSURE SIDE WITH A REFRIGERANT CONTAINER CONNECTED TO THE SYSTEM! OPENING THE HIGH PRESSURE SIDE WILL OVERPRESSURIZE THE CAN, CAUSING IT TO EXPLODE! Always wear safety goggles when working on a system to protect the eyes. If refrigerant contacts the eye, it is advisable in all cases to see a physician as soon as possible.

Fig. 47 Lower pressure valve located on the accumulator 5. Operate the pump until the low pressure gauge reads 28 inches Hg. Continue running the vacuum pump for at least 15 minutes. If you have replaced some component in the system, run the pump for an additional 30 minutes. 6. Close the valves and turn the pump off. The needle should remain stationary at the point at which the pump was

1. Connect an approved R-12 Recovery/Recycling machine to the valves and follow the instructions provided with the unit. 2. Open the R-12 source valve and allow 1 lb. of of liquid R-12 to flow into the system through the low side fitting. 3. Turn on the A/C system and allow the compressor operation to draw in the remainder of the preset amount of R-12 into the system. 4. Turn off the source valve and run the engine for 30 seconds to clear the lines and gauges. 5. Quickly unscrew the adaptors and recap the fittings. 6. Leak check the system and check for proper performance.

LEAK TESTING Look for trails left where refrigerant has flowed and test the suspect fitting with soapy water. There must be at least a 1 |b. charge in the system for a leak to be detected. The most extensive leak tests are performed using an electronic leak tester. Follow the instruction provided with the unit when using the leak checker.

~

ROUTINE MAINTENANCE

1-25

Troubleshooting Basic Air Conditioning Problems Problem

There ¢ little or no air coming from the vents (and you're sure it's on)

Solution

Cause

* The AC fuse is blown + Broken or loose wires or connec-

* Check andor replace fuse + Check andor repair connections

tions

The air corwng from the vents is not COO; enougn }

* The on off switch is defective

* Replace switch

* Windows and air vent wings open

+ « *

- The compressor bett is slipping

* Heater is on * Condenser is clogged with debris - Refrigerant has escaped through a leak in the system

Close windows and vent wings Tighten or replace compressor belt Shut heater off Clean the condenser Check system

- Receiver drier is plugged

- Service system

- Vacuum system is disrupted

- Have the system checked/repaired + Clean the evaporator case

- Odor producing substances on the eVApOrator Case

Sysiem is noisy or woraing

- Condensation has collected in the potiom of the evaporator nousing

* Clean the evaporator housing

- Compressor belt or mountings

- Tighten or replace belt; tighten

- Air in the system

mounting bolts - Have the system serviced

+ Undercharged system

+ Charge the system

- No refrigerant at all - System is OK

* Check and charge the system

+ Receiver drier is leaking dessicant

* Have system checked

* System undercharged

- Charge and leak test the system

+ Broken valves

- Replace the valve plate

- Overcharged

- Discharge, evacuate and install the

* Incorrect oil level

correct charge * Isolate the compressor and check

- Piston slap - Broken rings

the oi! level. Correct as necesSary. + Replace the compressor - Replace the compressor

WOSE

Sight glass condition Consiam bubbles. foam or oil

drains

Sireaxs

Clear sight glass. but no cold air Cleas sight glass. but air is cold

INES

Compressor noise

Excessive vibration

- Drive belt pulley bolts are loose

- Tighten with the correct torque specification

- Incorrect belt tension

+ Adjust the belt tension * Tighten the clutch * Discharge, evacuate and install the correct charge - Align the pulley

+ Clutch loose

- Overcharged

- Pulley is misaligned

Condensation dripping in the passenger compartment

; Drain hose plugged or improperly positioned

- insulation removed or improperty installed

- Clean the drain hose and check for proper installation * Replace the insulation on the expansion valve and hoses B571T1029

1-26

ROUTINE MAINTENANCE Troubleshooting Basic Air Conditioning Problems (cont.)

Frozen evaporator coil

Low side low—high side low

Low side high—high side low

S olution

Cause

Problem

- Faulty thermostat - Thermostat capillary tube improperly installed - Thermostat not adjusted properly

Replace the thermostat - Install the capillary tube correctly

- System refrigerant is low

- Evacuate, leak test and charge the

- Expansion valve is restricted

- Replace the expansion valve

- Internal leak in the compressor—

- Remove the compressor cylinder head and inspect the compressor. Replace the valve plate assembly if necessary. If the _ compressor pistons, rings or

system

worn

Low side high—high side low (cont.)

- Cylinder head gasket is leaking

Low side high—high side high

- Adjust the thermostat

cylinders are excessively worn or scored replace the compressor - Install a replacement cylinder head gasket

- Expansion valve is defective * Drive belt slipping

- Replace the expansion valve + Adjust the belt tension

- Condenser fins obstructed - Airin the system

* Clean the condenser fins - Evacuate, leak test and charge the

- Expansion valve is defective - Loose or worn fan belts

- Replace the expansion valve - Adjust or replace the belts as nec-

system

essary Low side low—high side high

- Expansion valve is defective - Restriction in the refrigerant hose

- Replace the expansion valve - Check the hose for kinks—replace if necessary

Low side low—high side high

- Restriction in the receiver drier * Restriction in the condenser

- Replace the receiver/drier - Replace the condenser

Low side and high normal (inadequate cooling)

Air in the system

- Moisture in the system

Evacuate, leak test and charge the system - Evacuate, leak test and charge the

system 85771040

Windshield Wipers REFILL REPLACEMENT » See Figure 48 For maximum effectiveness and longest element life, the windshield and wiper blades should be kept clean. Dirt, tree

sap, road tar and so on will cause streaking, smearing and blade deterioration if left on the glass. It is advisable to wash the windshield carefully with a commercial glass cleaner at least once a month. Wipe off the rubber blades with the wet rag afterwards. Do not attempt to move the wipers back and

forth by hand; damage to the motor and drive mechanism will result.

If the blades are found to be cracked, broken or torn, they should be replaced immediately. Replacement intervals will vary with usage, although normal weathering usually limits blade life to about one year. If the wiper pattern is smeared or streaked, or if the blade chatters across the glass, the blades should be replaced. It is easiest and most sensible to replace them in pairs. There are basically three different types of wiper blade refills, which differ in their method of replacement. One type has two release buttons, approximately 1/3 of the way up from the ends of the blade frame. Pushing the buttons down releases a lock and allows the rubber blade to be removed from the

ROUTINE MAINTENANCE — 1-27 frame. The new blade slides back into the frame and locks in place.

The tires on your truck will have built-in tread wear indicators, which appear as ‘2 inch bands when the tread depth gets as low as ‘/i¢ in. When the indicators appear in 2 or more adjacent grooves, it’s time for new tires. For optimum tire life, you should keep the tires properly inflated, rotate them often and have the wheel alignment checked periodically. Some late models have the maximum load pressures listed on the V.I.N. plate on the left door frame. In general, pressure of 28-32 psi would be suitable for highway use with moderate loads and passenger car type tires (load range B, non-flotation) of original equipment size. Pressures should be checked before driving, since pressure can increase as much as 6 psi due to heat. It is a good idea to have an accurate gauge and to check pressures weekly. Not all gauges on service station air pumps are to be trusted.

The second type of refill has two metal tabs which are unlocked by squeezing them together. The rubber blade can then be withdrawn from the frame jaws. A new one is installed by inserting it into the front frame jaws and sliding it rearward fo engage the remaining frame jaws. There are usually four jaws; be certain when installing that the refill is engaged in all of them. At the end of its travel, the tabs will lock into place on the front jaws of the wiper blade frame. The third type is a refill made from polycarbonate. The refill has a simple locking device at one end which flexes downward out of the groove into which the jaws of the holder fit, allowing easy release. By sliding the new refill through all the jaws and pushing through the slight resistance when it reaches the end of its travel, the refill will lock into position. Regardless of the type of refill used, make sure that all of the frame jaws are engaged as the refill is pushed into place and locked. The metal blade holder and frame will scratch the glass if allowed to touch it.

TIRE ROTATION » See Figure 52

Tires and Wheels

It is recommended that you have the tires rotated every 6,000 miles. There is no way to give a tire rotation diagram for every combination of tires and vehicles, but the accompanying diagrams are a general rule to follow. Radial tires should not

» See Figures 49, 50 and 51 The tires should be rotated as specified in the Maintenance Intervals chart. Refer to the accompanying illustrations for the

be cross-switched; they last longer if their direction of rotation

is not changed. Truck tires sometimes have directional tread, indicated by arrows on the sidewalls; the arrow shows the direction of rotation. They will wear very rapidly if reversed.

recommended rotation patterns.

RUBBER BLADE ELEMENT ASSY

LEVER JAWS

SQUEEZE SIDES OF RETAINER

LATCH LOCK RELEASE

METAL BACKING IS WIDER

HOLD FRAME FROM TWISTING

METAL BACKING STRIP

RETAINING TABS

INSERT SCREWDRIVER BEHIND TAB AND PUSH

LATCH-PIN

AUBBER BLADE ELEMENT ASSY YOKE JAWS

POLYCARBOMATE

=

= 85771041

Fig. 48 The three types of wiper blade retention

1-28

ROUTINE MAINTENANCE TIRE DESIGN TREAD STILL GOOD

ES

85771042

Fig. 49 Tire tread wear indicators appear as solid bands when the tire is worn out

85771043

Fig. 50 Tread depth can be checked with a penny; when the top of Lincoln’s head is visible, it’s time for new tires

eee

The tires on your truck were selected to provide the best allaround performance for normal operation when inflated as specified. Oversize tires (Load Range D) will not increase the maximum carrying capacity of the vehicle, although they will provide an extra margin of tread life. Be sure to check overall height before using larger size tires which may cause interference with suspension components or wheel wells. When replacing conventional tire sizes with other tire size designations, be sure to check the manufacturer's recommendations. Interchangeability is not always possible because of differences in load ratings, tire dimensions, wheel well clearances, and rim size. Also due to differences in handling characteristics, 70 Series and 60 Series tires should be used only in pairs on the same axle; radial tires should be used only in sets of four. The wheels must be the correct width for the tire. Tire dealers have charts of tire and rim compatibility. A mismatch can cause sloppy handling and rapid tread wear. The old rule of thumb is that the tread width should match the rim width (inside bead to inside bead) within an inch. For radial tires, the rim width should be 80% or less of the tire (not tread) width. The height (mounted diameter) of the new tires can greatly change speedometer accuracy, engine speed at a given road speed, fuel mileage, acceleration, and ground clearance. Tire manufacturers furnish full measurement specifications. Speedometer drive gears are available for correction. =>Dimensions of tires marked the same size may vary significantly, even among tires from the same manufacturer. The spare tire should be usable, at least for low speed operation, with the new tires. For maximum satisfaction, tires should be used in sets of

85771044

Fig. 51 Tread depth can also be checked with and inexpensive gauge made for the purpose Studded snow tires will lose their studs if their direction of rotation is reversed.

five. Mixing or different types (radial, bias-belted, fiberglass belted) should be avoided. Conventional bias tires are constructed so that the cords run bead-to-bead at an angle. Alternate plies run at an opposite angle. This type of construction gives rigidity to both tread and sidewall. Bias-belted tires are similar in construction to conventional bias ply tires. Belts run at an angle and also at a 90 degree angle to the bead, as in the radial tire. Tread life is improved considerably over the conventional bias tire. The radial tire differs in construction, but

instead of the carcass plies running at an angle of 90 degree to each other, they run at an angle of 90 degree to the bead. This gives the tread a great deal of rigidity and the sidewall a

->\Vark the wheel position or direction of rotation on radial tires or studded snow tires before removing them. If your truck is equipped with tires having different load ratings on the front and the rear, the tires should not be rotated front to rear. Rotating these tires could affect tire life (the tires with the lower rating will wear faster, and could become overloaded), and upset the handling of the truck.

LF

|REE

RF

LR O)} IRR LR S WHEEL ROTATION

RR

4 WHEEL ROTATION 85771045

Fig. 52 This rotation pattern is for radial tires; it can also be used for bias tires. The spare tire can be used on the left side too, but don’t change it’s direction of

rotation once used.

;

ROUTINE MAINTENANCE Chevrolet and GMC trucks are capable of using and they are recommended in some years. If they tire sized and wheel diameters should be selected ground clearance and tire load capacity equivalent mum specified tire.

1-29 radial tires are used, to maintain to the mini-

Radial tires should never be used on only the front axle. BIAS PLY TIRE 4 WHEEL ROTATION

BIAS PLY TIRE 5 WHEEL ROTATION

85771046

Radial tires must not be mounted on 16.5 inch rims unless the rims are stamped with the word Radial. Ordinary rims are not strong enough to withstand the additional side loads.

Fig. 53 This rotation pattern is for bias tires only

On four wheel drive trucks, all tires must be of the same size, type, and tread pattern, to provide even traction on loose

great deal of flexibility and accounts for the characteristic bulge

Surfaces, to prevent driveline bind when conventional four

associated with radial tires.

wheel drive is used, and to prevent excessive wear on the center differential with full time four wheel drive.

Troubleshooting Basic Wheel Problems Problem

Cause

Solution

The car's front end vibrates at high speed

- The wheels are out of balance - Wheels are out of alignment

- Have wheels balanced * Have wheel alignment checked/adjusted

Car pulls to either side

- Wheels are out of alignment

* Have wheel alignment checked/adjusted - Check/adjust tire pressure - Change tires or wheels to same size

- Unequal tire pressure - Different size tires or wheels

The car's wheel(s) wobbles

+ Loose wheel lug nuts - Wheels out of balance - Damaged wheel

- Wheels are out of alignment - Worn or damaged ball joint - Excessive play in the steering linkage (usually due to worn parts) - Defective shock absorber Tires wear unevenly or prematurely

- Incorrect wheel size

- Wheels are out of balance - Wheels are out of alignment

* Tighten wheel lug nuts - Have tires balanced - Raise car and spin the wheel. If the wheel is bent, it should be replaced - Have wheel alignment checked/adjusted * Check ball joints + Check steering linkage

* Check shock absorbers - Check if wheel and tire size are compatible - Have wheels balanced - Have wheel alignment checked/adjusted

eam

85771048

1-30

ROUTINE MAINTENANCE Tire Size Comparison Chart

“60 Series’’

“70 Series”

“78 Series”

1965-77

“60 Series”

“70 Series”

“80 Series”

5.50-12, 5.60-12 6.00-12

165/60-12

165/70-12

155-12

Y78-12

5.20-13 5.60-13 6.15-13 6.40-13 6.70-13 6.90-13 7.00-13 7.25-13 7.75-13

165/60-13 175/60-13 185/60-13 195/60-13 205/60-13

145/70-13 155/70-13 165/70-13 175/70-13 185/70-13

135-13 145-13 155-13, P155/80-13 165-13 175-13

215/60-13

195/70-13

185-13

W78-13 Y78-13 A60-13 B60-13

A70-13 B70-13

A78-13 B78-13

C60-13 D60-13 E60-13

C70-13 D70-13 E70-13

C78-13 D78-13 E78-13

A60-14

D60-14 E60-14 F60-14 G60-14 H60-14 J60-14 L60-14 B60-15 C60-15 E60-15 F60-15 G60-15 H60-15 J60-15 L60-15

Metric-inch Sizes

Inch Sizes

“Letter” sizes

A70-14 B70-14 C70-14 D70-14 E70-14 F70-14 G70-14 H70-14 J70-14 L70-14

A78-14 B78-14 C78-14 D78-14 E78-14 F78-14, F83-14 G77-14, G78-14 H78-14 J78-14

A70-15 B70-15 C70-15 D70-15 E70-15 F70-15 G70-15 H70-15 J70-15 K70-15 L70-15 M70-15

A78-15 B78-15 C78-15 D78-15 E78-15 F78-15 G78-15 H78-15 J78-15 L78-15, L84-15 M78-15 N78-15

195-13

5.20-14 5.60-14 5.90-14 6.15-14 6.45-14 6.95-14

165/60-14 175/60-14

145/70-14 155/70-14

135-14 145-14

185/60-14 195/60-14 205/60-14

165/70-14 175/70-14 185/70-14

155-14 165-14 175-14

7.35-14 7.75-14 8.25-14 8.55-14 8.85-14 9.15-14

215/60-14 225/60-14 235/60-14 245/60-14 255/60-14 265/60-14

195/70-14 200/70-14 205/70-14 215/70-14 225/70-14 235/70-14

185-14 195-14 205-14 215-14 225-14

5.60-15 6.35-15 6.85-15

185/60-15 195/60-15 205/60-15

165/70-15 175/70-15 185/70-15

155-15 165-15 175-15

7.35-15 7.75-15 8.15-15/8.25-15 8.45-15/8.55-15 8.85-15/8.90-15 9.00-15 9.15-15

215/60-15 225/60-15 235/60-15 245/60-15 255/60-15 265/60-15

195/70-15 205/70-15 215/70-15 225/70-15 235/70-15 245/70-15

185-15 195-15 205-15 215-15 225-15 230-15 235-15 255-15

NOTE: Every size tire is not listed and many size coma prisons are approximate, based on load ratings. Wider tires than those supplied new with the vehicle should always be checked for clearance 85771050

ROUTINE MAINTENANCE — 1-31

Troubleshooting Basic Tire Problems SSS

Problem

SSS

Cause

Solution

The car's front end vibrates at high speeds and the steering wheel shakes

+ Wheels out of balance

- Have wheels balanced

* Front end needs aligning

- Have front end alignment checked

The car pulls to one side while cruising

- Unequal tire pressure (car will usually pull to the low side) - Mismatched tires

- Check/adjust tire pressure

» Front end needs aligning Abnormal, excessive or uneven tire wear

- Infrequent tire rotation

- Be sure tires are of the same type and size - Have front end alignment checked

- Improper tire pressure

- Rotate tires more frequently to equalize wear - Check/adjust pressure

- Sudden stops/starts or high speed

* Correct driving habits

See “How to Read Tire Wear” on curves

Tire squeals

+ Improper tire pressure

- Front end needs aligning

- Check/adjust tire pressure - Have front end alignment checked 85771049

TIRE STORAGE

CARE FOR ALUMINUM WHEELS

Store the spare tire AND ALL ACCESSORIES in their proper places. Leaving them out invites damage and noise. Store the tires at proper inflation pressure if they are mounted on wheels. All tires should be kept in a cool, dry place. If they are stored in the garage or basement, do not let them stand on a concrete floor; set them on strips of wood.

Aluminum wheels should be cleaned and waxed regularly with products developed specifically for aluminum products. Read the label of any product you are considering using prior to application. Do not use abrasive cleaners because they may damage the protective coating.

FLUIDS AND LUBRICANTS Fluid Disposal Used fluids, such as engine oil, antifreeze, transmission oils and brake fluid are hazardous as waste material and must be disposed of properly. Before draining any fluids, consult with your local municipal government. In may areas, waste oils are being accepted as part of the recycling program. A number of service stations, repair facilities and auto parts stores are accepting these waste fluids for recycling. Be sure of the recycling center's policies before draining any fluids, as many will not accept different fluids that have been mixed together, such as oil and antifreeze.

; Fuel and Engine Oil Recommendations MOTOR OIL General Information

The SAE grade number indicates the viscosity of the engine oil, or its ability to lubricate under a given temperature. The lower the SAE grade number, the lighter the oil; the lower the viscosity, the easier it is to crank the engine in cold weather.

The API (American Petroleum Institute) designation indicates the classification of engine oil for use under given operating conditions. Only oils designated for Service SF should be used. These oils provide maximum engine protection. Both the

1-32.

ROUTINE MAINTENANCE

SAE grade number and the API designation can be found on the top of a can of oil. =>Non-detergent oil should not be used.

Oil viscosities should be chosen from those oils recommended for the lowest anticipated temperatures during the oil change interval. The multi-viscosity oils offer the important advantage of being adaptable to temperature extremes. They allow easier starting at cold engine temperatures. This is a decided advantage in changeable climates or in long distance driving. Diesel engines also require SF engine oil. In addition, the oil must qualify for a CC rating. The API has a number of different diesel engine ratings, including CB, CC, and CD. s>1981 and later diesel engines can use either SF/CC, SF/CD.

The diesel engine in the Chevrolet and GMC pick-ups requires SF/CC rated oil. DO NOT use an oil if the designation CD appears anywhere on the oil can. Use SF/CC engine oil only. Do not use an oil labeled only SF or only CC. Both designations must appear. For recommended oil viscosities, refer to the chart. 10W-30 grade oils are not recommended for sustained high speed driving. Single viscosity, oil (SAE 30) is recommended for sustained high speed driving. Gasoline Engine Oil Viscosity Chart

(© Chevrolet Motor Div.) NOTES:

1. SAE mended 2. SAE seasons

5W and 5W-20 are not recomfor sustained high speed driving. 5W-30 Is recommended for all in Canada

85771051

Synthetic Oil

There are excellent synthetic and fuel-efficient oils available that, under the right circumstances, can help provide better fuel mileage and better engine protection. However, these advantages come at a price, which can be three or four times the price per quart of conventional motor oils. Before pouring any synthetic oils into your car's engine, you should consider the condition of the engine and the type of driving you do. Also, check the truck’s warranty conditions regarding the use of synthetics. Generally, it is best to avoid the use of synthetic oil in both brand new and older, high mileage engines. New engines require a proper break-in, and the synthetics are so slippery that they can prevent this; most manufacturers recommend that you wait at least 5,000 miles before switching to a synthetic oil. Conversely, older engines are looser and tend to use more oil; synthetics will slip past worn parts more readily than regular oil, and will be used up faster. If your vehicle already leaks and/or uses oil (due to worn parts and bad seals or gaskets), it will leak and use more with a slippery synthetic inside. Consider your type of driving. If most of your accumulated mileage is on the highway at higher, steadier speeds, a synthetic oil will reduce friction and probably help deliver better fuel mileage. Under such ideal highway conditions, the oil change interval can be extended, as long as the oil filter will operate effectively for the extended life of the oil. If the filter can’t do its job for this extended period, dirt and sludge will build up in your engine’s crankcase, sump, oil pump and lines, no matter what type of oil is used. If using synthetic oil in this manner, you should continue to change the oil filter at the recommended intervals. Trucks used under harder, stop-and-go, short hop circumstances should always be serviced more frequently, and for these trucks synthetic oil may not be a wise investment. Because of the necessary shorter change interval needed for this type of driving, you cannot take advantage of the long recommended change interval of most synthetic oils. Finally, most synthetic oils are not compatible with conventional oils and cannot be added to them. This means you should always carry a couple of quarts of synthetic oil with you while on a long trip, as not all service stations carry this oil.

FUELS

Diesel Engine Oil Viscosity Chart Gasoline Engines

USE THESE SAE VISCOSITY GRADES (SE/CC)

10

0

TEMPERATURE RANGE YOU EXPECT BEFORE NEXT OIL CHANGE 85771052

Chevrolet and GMC trucks with Gross Vehicle Weight Ratings (GVWR) which place them in the heavy duty emissions class do not require a catalytic converter. However, all 1980-87 light duty emissions trucks have a catalytic converter. In 1980-87, the light duty classification applies to all trucks with GVWR’s under 8,600 Ibs. The catalytic converter is a muffler-shaped device installed in the exhaust system. It contains platinum and palladium coated pellets which, through catalytic action, oxidize hydrocarbon and carbon monoxide gases into hydrogen, oxygen, and carbon dioxide. The design of the converter requires the exclusive use of unleaded fuel. Converter equipped trucks are delivered with the label Unleaded Fuel Only placed next to the fuel gauge on the instru-

ROUTINE MAINTENANCE ment panel and next to the gas tank filler opening. In general, any unleaded fuel is suitable for use in these trucks as long as the gas has an octane rating of 87 or more. Octane ratings are posted on the gas pumps. However, in some cases, knocking may occur even though the recommended fuel is being used. The only practical solution for this is to switch to a slightly higher grade of unleaded fuel, or to switch brands of unleaded gasoline. e*Your engine’s fuel requirement can change with time, mainly due to carbon buildup, which changes the compression ratio. If your engine pings, knocks, or runs on, switch to a higher grade of fuel and check the ignition timing as soon as possible. If you must use unleaded fuel, sometimes a change of brands will cure the problem. If it is necessary to retard the timing from specifications, don’t change it more than about four degrees. Retarded timing will reduce power output and fuel mileage, and it will increase engine temperature. Diesel Engines Diesel engine pick-ups require the use of diesel fuel. Two grades of diesel fuel are manufactured, No. 1 and No. 2,

although No. 2 grade is generally the only grade available. Better fuel economy results from the use of No. 2 grade fuel. In some northern parts of the U.S., and in most parts of Canada, No. 1 grade fuel is available in winter, or a winterized blend of No. 2 grade is supplied in winter months. If No. | grade is available, it should be used whenever temperatures fall below 20°F (-7°C). Winterized No. 2 grade may also be used at these temperatures. However, unwinterized No. 2 grade should not be used below 20°F (-7°C). Cold temperatures cause unwinterized No. 2 grade to thicken (it actually gels), blocking the fuel lines and preventing the engine from running.

1-33

2s Wipe the dipstick with a clean rag.

4,573. Insert the dipstick fully into the tube, and remove it “again. Hold the dipstick horizontally and read the oil level. The level should be between the “FULL and “ADD OIL‘ marks. If the oil level is at or below the “ADD OIL” mark, oil should be added as necessary. Oil is added through the capped opening on the valve cover(s) on gasoline engines. Diesel engines have a capped oil fill tube at the front of the engine. See Oil and Fuel Recommendations for the proper viscosity oil to use. 4. Replace the dipstick and check the level after adding oil. Be careful not to overfill the crankcase. Approximately one quart of oil will raise the level from “ADD” to “FULL’.

OIL AND FILTER CHANGE » See Figures 58, 59, 60, 61, 62, 63 and 64 Engine oil should be changed according to the schedule in the Maintenance Interval Chart. Under the following conditions the oil should be changed more frequently : e Driving in dusty conditions, e Continuous trailer pulling or RV use, e Extensive or prolonged idling, e Extensive short trip operation in freezing temperatures (when the engine is not thoroughly warmed-up), e Frequent long runs at high speeds and high ambient temperatures.

Do not use home heating oil or gasoline in the diesel pick-up. Do not attempt to thin unwinterized No. 2 diesel fuel with gasoline. Gasoline or home heating oil will damage the engine and void the manufacturer’s warranty. 85771053

OIL LEVEL CHECK

Fig. 54 Check engine crankcase oil level with the dipstick

» See Figures 54, 55, 56 and 57 The engine oil should be checked on a regular basis, ideally at each fuel stop. If the truck is used for trailer towing or for heavy duty use, it would be safer to check it more often. When checking the oil level it is best that the oil be at operating temperature, although checking the level immediately after stopping will give a false reading because all of the oil will not yet have drained back into the crankcase. Be sure that the truck is resting on a level surface, allowing time for the oil to drain back into the crankcase. 1. Open the hood and locate the dipstick. Remove it from the tube. The oil dipstick is located on the passenger’s side of 6 cylinder engines and on the driver's side of V8s.

85771054

Fig. 55 The oil level should show between the “AD” and “FULL” marks on the dipstick

1-34

ROUTINE MAINTENANCE

Fig. 56 One of the valve covers should be equipped with a capped oil filler opening

Fig. 58 The oil drain plug is located at the lowest point of the engine oil pan. Use a ratchet and socket or a box wrench to loosen the plug

85771055

Fig. 57 To help prevent spilling and wasting oil when filling, use a funnel to pour oil in the valve cover opening

85771097

Fig. 59 Loosen the drain plug by hand while using thumb pressure to keep oil from dripping

e Stop-and-go service such as delivery trucks,the oil change interval and filter replacement interval should be cut in half. Operation of the engine in severe conditions such as a dust storm may require an immediate oil and filter change. Chevrolet and GMC recommended changing both the oil and filter during the first oil change and the filter every other oil change thereafter. For the small price of an oil filter, it's cheap insurance to replace the filter at every oil change. One of the larger filter manufacturers points out in its advertisements that not changing the filter leaves one quart of dirty oil in the engine. This claim is true and should be kept in mind when changing your oil.

=The oil filter on the diesel engines must be changed every oil change.

85771098

Fig. 60 Quickly withdraw the plug and keep out of the way of the hot oil stream

To change the oil, the truck should be on a level surface, and the engine should be at operating temperature. This is to ensure that the foreign matter will be drained away along with the oil, and not left in the engine to form sludge. You should have available a container that will hold a minimum of 8 quarts of liquid, a wrench to fit the old drain plug, a spout for pouring in new oil, and a rag or two, which you will always need. If the filter is being replaced, you will also need a band wrench or filter wrench to fit the end of the filter.

2. From under the truck, loosen, but do not remove the oil drain plug using a ratchet and socket or a box wrench. 3. Carefully unscrew the drain plug by hand while applying thumb pressure to hold the plug back in position. The pressure will prevent oil from oozing past the drain plug until it is fully withdrawn. Keep a rag handy to quickly wipe off any hot oil which may splash on you.

elf the engine is equipped with an oil cooler, this will also have to be drained, using the drain plug. Be sure to add enough oil to fill the cooler in addition to the engine.

The engine oil will be HOT. Keep your arms, face and hands clear of the oil as it drains out.

1. Position the truck on a level surface and set the parking brake or block the wheels. Slide a drain pan under the oil drain plug.

4. Once the plug is completely loosened, quickly withdraw the plug and move your hand with the rag away from the

“sk CAUTION

ROUTINE MAINTENANCE — 1-35 SL

ES

SIENA

ST

AL

SI

EC

ESSE

SSE

SS

ES

BT

ESS

SET

NIC

SR

OSA

SETS TO

stream of hot oil. Allow the oil to completely drain into the pan. ->Do not drop the plug into the drain pan.

5. When all of the oil has drained, clean off the drain plug and put it back into the hole. Make sure the gasket on the plug is in place and in good condition prior to installing it into the oil pan. Tighten the drain plug on a gasoline engine to 20 ft. Ibs. If equipped with a diesel engine, tighten the drain plug to 30 ft. Ibs. 6. Loosen the filter with a band wrench or special oil filter cap wrench. On most Chevrolet engines, especially the V8s, the oil filter is next to the exhaust pipes. Use caution when working near hot exhaust components, since even a passing contact will result in a painful burn.

Fig. 63 Coat the gasket on the new oil filter with a film of clean engine oil

CAUTION On trucks equipped with catalytic converters stay clear of the converter. The outside temperature of a hot catalytic converter can approach 1200 degrees F. 7. Cover your hand with a rag, and spin the filter off by hand. Spin the filter and few turns, then remove your hand as some of the oil will flow down the sides. When you unscrew the filter the rest of the way, be careful to keep it vertical as it still contains up to a quart of oil.

Confirm that the O-ring from the oid oil filter was removed with the old oil filter. If still attached to the adapter when the new oil filter and O-ring are installed, an oil leak will occur.

85771100

Fig. 64 To prevent overtightening, always install the new filter by hand 8. Coat the rubber gasket on a new filter with a light film of clean engine oil. Screw the filter onto the mounting stud and tighten according to the directions on the filter (usually hand tight one turn past the point where the gasket contacts the mounting base). Don’t overtighten the filter. 9. Refill the engine with the specified amount of clean engine oil. 10. Run the engine for several minutes, checking the leaks. Check the level of the oil and add oil, if necessary.

Manual Transmission 85771057

Fig. 61 Only use a strap wrench to loosen the old oil filter

.

FLUID RECOMMENDATIONS The correct lubricant to use in the manual transmission varies depending on model year and transmission. Refer to the list below for the lubricant that should be used in your vehicle. In some instances you must know the RPO code for the transmission in your truck. This code can be found on the Service Parts Identification label located on glove box door or on the fenderwell. 1980-81 e Use SAE 80W-90 GL-5 gear lubricant or SAE 80W GL-5 in colder climates. 1982-85

85771099

Fig. 62 Back the oil filter a few turns, then remove your hand as some of the old oil will flow over the sides

1-36

ROUTINE MAINTENANCE

e On all manual transmissions except the 4 speed with

overdrive, use SAE 80W-90 GL-5 gear lubricant or SAE 80W GL-5 in colder climates. e On the 4 speed manual transmission with overdrive, use DEXRON@®II

1986 ; e On all manual transmissions except the 4 speed with overdrive and the 5 speed, use SAE 80W-90 GL-5 gear lubricant or SAE 80W GL-5 in colder climates. e On the 4 speed manual! transmission with overdrive or the 5 speed manual, use DEXRON®|

1987 e On 3 speed manual transmissions with RPO M62 or M60 and 4 speed manual transmissions with RPO M20, use SAE 80W-90 GL-5 gear lubricant or SAE 80W GL-5 in colder climates. e On 4 speed manual transmissions with RPO MCO and without the creeper gear or 5 speed manual transmissions with RPO MG5, use GM Manual Transmission Fluid part no.

1052931. e On 4 speed manual transmissions with overdrive (RPO MY6) or 5 speed manual transmissions with RPO ML2, ML3 or MH3, use DEXRON@III.

LEVEL CHECK Check the lubricant level at the interval specified in the maintenance chart. 1. With the truck parked on a level surface, remove the filler plug from the side of the transmission case. Be careful not to take out the drain plug at the bottom. 2. If lubricant begins to trickle out of the hole, there is enough. If not, carefully insert a finger (watch out for sharp threads) and check that the level is up to the edge of the hole. 3. If not, add sufficient lubricant with-a funnel and tube, or a squeeze bulb to bring it to the proper level. 4. Replace the plug and check for leaks.

DRAIN AND REFILL

6. Add the correct lubricant with a suction gun or squeeze bulb. 7. Reinstall the filler plug. Run the engine and check for leaks.

Automatic Transmissions

FLUID RECOMMENDATIONS The correct fluid to use in the automatic transmission is DEXRON®II.

LEVEL CHECK » See Figure 65 Check the level of the fluid at the specified interval. The fluid level should be checked with the engine running and at normal operating temperature. If the truck has been running at high speed for a long period, in city traffic on a hot day, or pulling a trailer, let it cool down for about thirty minutes before check-

ing the level. 1. Park on a level surface with the engine running and the shift lever in Park. 2. Remove the dipstick at the rear of the engine compartment. Cautiously feel the end of the dipstick with your fingers. Wipe it off and replace it, then pull it again and check the level of the fluid on the dipstick. 3. If the fluid felt cool, the level should be between the two dimples below ADD. If it was too hot to hold, the level should be between the ADD and FULL marks. 4. If the fluid is at or below the ADD mark, add fluid

through the dipstick tube. One pint raises the level from ADD to FULL when the fluid is hot. The correct fluid to use is DEXRON®Il. Be certain that the transmission is not overfilled; this will cause foaming, fluid loss, and slippage.

DRAIN AND REFILL » See Figure 66

On 1986 and 1987 trucks equipped with the four speed (RPO M73) transmission, four speed transmission with overdrive, or the five speed transmission the transmission lubricant should be changed every 30,000 miles (50 km). No intervals are specified for changing the transmission lubricant for trucks built prior to1985, but it is a good idea on a used vehicle, one that has been worked hard, or one driven in deep water. The vehicle should be on a level surface and the lubricant should

Some automatic transmissions are equipped with drain plugs to facilitate fluid changes, but most transmissions require that the pan be removed in order to drain the fluid. This is done

(65° -85°F.) coot

be at operating temperature.

1. Position the truck on a level surface. 2. Place a pan of sufficient capacity under the transmission drain plug. 3. Remove the upper (fill) plug to provide a vent opening. 4. Remove the lower (drain) plug and let the lubricant drain out. The 1980 Tremec top cover three speed transmission is drained by removing the lower extension housing bolt. 5. Replace the drain plug.

NOTE:

(18° -29°C.) HOT

T . It takes only one pint to roise level from ADD to FULL with a hot transmission. 85771060

Fig. 65 Automatic transmission dipstick markings

ROUTINE MAINTENANCE — 1-37 partially to discourage fluid changes without changing the filter. Complete draining and refilling instructions can be found as part of the filter change procedure in Section 7 of this manual.

Transfer Case

FLUID RECOMMENDATIONS The type of lubricant used in the transfer case varies with model year and type of transfer case. Refer to the list below for the type that applies to your truck. 1980 e Conventional transfer cases require SAE 80W or SAE 80W-90 GL-5 gear lubricant. e Full time systems use SAE 10W-30 or 10W-40 engine oil. 1981 e Conventional transfer cases require DEXRON®)I transmission fluid. 1982-85 e All transfer cases require DEXRON®II transmission fluid. 1986-87 e All transfer cases except the K30/35 series require DEXRON@®II transmission fluid. e For fluid recommendations for the K30/35 transfer cases refer to the owner’s manual.

LEVEL CHECKS » See Figure 67 Check the four wheel drive transfer case lubricant level every 4 months or 6,000 miles. 1. With the truck parked on a level surface and the parking brake firmly applied, remove the filler plug from the rear of the transfer case (behind the transmission). Be careful not to take out the drain plug at the bottom. 2. If lubricant trickles out, there is enough. If not, carefully insert a finger and check that the level is up to the edge of the hole, EXCEPT in full time four wheel drive cases should be ‘2 in. below the hole. Lubricant may be added, if necessary, with a funnel and tube, or a squeeze bulb.

THe V4 5

ANS é

:

INDICATOR SWITCH 85771062

Fig. 67 Model 208 Transfer Case

DRAIN AND REFILL Part Time Systems No intervals are specified for changing transfer case lubricant, but it is a good idea for trucks that are worked hard or driven in deep water. 1. With the transfer case warmed up, park on a level surface and apply the parking brake. 2. Slide a pan of a least 6 pts. capacity under the case drain plug. 3. Remove the filler plug from the rear of the transfer case (behind the transmission). Remove the drain plug from the bottom. 4, Wipe the area clean and replace the drain plug. 5. Add lubricant with a suction gun or squeeze bulb. Conventional transfer cases require SAE 80W-90 GL-5 Gear Lubricant. 6. When the lubricant level is up to the bottom of the filler hole, replace the plug. Full Time Four Wheel: Drive

The full time system requires oil changes at regular intervals, according to the amount and type of work done by the unit. Trucks used for normal on-off road work should have the transfer case oil changed at 24,000 mile intervals. When used for heavy duty work, trailer towing, snowplowing, and the like, the interval should be halved to 12,000 miles. If the truck is exposed to extremely dusty or muddy conditions, the oil should be changed at 1,000 mile intervals. The transfer case oil must be hot before changing. Drive the truck until the engine has reached normal operating temperature, and park on a level surface.

1. Slide a pan of at least 8 pts. capacity under the case

drain plug.

85771061

Fig. 66 Add automatic transmission fluid through the automatic transmission dipstick tube using a funnel

iii

2. Remove the filler plug. 3. Remove the lowest bolt from the front output shaft rear bearing retainer cover, and allow the lubricant to drain. Be careful; the oil will be hot. There may be a drain plug. If so, remove that instead. 4. Remove the six bolts on the left (driver's) side of the case which secure to P.T.O. (power take-off) cover. Remove this cover and allow the lubricant to drain out. 5. Remove the speedometer driven gear from the upper left rear corner of the case.

1-38 Ea

ROUTINE MAINTENANCE a

ES

6. Use a suction gun to remove as much lubricant as possible from the case cover location and the speedometer gear location. 7. Install the speedometer driven gear, the P.T.O. cover,

and the lowest bolt or drain plug. 8. Add approximately seven pints of oil through the filler plug opening. The proper oil to use is 10W-30 or 10W-40 engine oil. 9. Check the fluid level and add sufficient oil to raise the level to ‘2 in. below the filler plug opening. Replace the plug, and wipe the surfaces of the case and skid plate to remove any excess oil. Drive the truck and check for leaks.

“

y td

85771102

Fig. 70 The square plug may be removed by a standard

Drive Axle (Rear and/or Front)

ratchet extension 2. Place a pan of at least 6 pints capacity under the differ-

FLUID RECOMMENDATIONS

ential housing. 3. Remove the filler plug. 4. If you have a drain plug, remove it. If not, unbolt and

Front axles use SAE 80W-90, GL-5 Gear Lubricant. Rear axles use SAE 80W-90 gear oil. Positraction or locking axles must use special lubricant available from dealers. If the special

remove the differential cover. 5. Replace the drain plug, or differential cover. Use a new gasket if the differential cover has been removed.

fluid is not used, noise, uneven operation, and damage will

result. There is also a Positraction additive used to cure noise and slippage. Positraction axles or locking axles have an identifying tag, as well as a warning sticker near the jack or on the rear wheel well.

LEVEL CHECK » See Figures 68, 69 and 70 The fluid level in the front axle should be ‘2 in. below the

FILLER PLUG

filler plug opening. The fluid level in the rear axle should be up to the bottom of the filler plug opening. Lubricant may be added with a suction gun or squeeze bulb. 1. Park on level ground.

ae Fig. 68 The rear axle filler plug is located on the rear housing cover for some vehicles

2. Remove the filler plug from the differential housing

cover. 3. If lubricant trickles out there is enough. If not, carefully insert a finger and check that the level is up to the bottom of the hole. Locking front hubs should be run in the LOCK position for at least 10 miles each month to assure proper lubrication to the front axle.

DRAIN AND REFILL

» See Figures 71, 72, 73 and 74 1. Park the vehicle on the level with the axles at normal operating temperature.

wg

:

rarity

Fig. 69 On this vehicles, the rear axle filler plug is located on the side of the housing

ROUTINE MAINTENANCE

85771105

Fig. 71 On rear axle housing not equipped with a drain plug, the rear cover must be removed to drain the fluid

1-39

85771104

Fig. 74 Once fluid begins to trickle oil, install the plug back into the bore

LEVEL CHECK » See Figures 75, 76, 77, 78 and 79

85771106

Fig. 72 Once all retaining bolts are removed, pry the bottom of the cover back to break the gasket seal

The coolant level should be checked at each fuel stop, ideally, to prevent the possibility of overheating and serious engine damage. If not, it should at least be checked once each month. The cooling system was filled at the factory with a high quality coolant solution that is good for year around operation and protects the system from freezing down to -20°F (-32°F in Canada). It is good for two full calendar years or 24,000 miles, whichever occurs first, provided that the proper concentration of coolant is maintained. The cooling system incorporates a plastic expansion tank connected to the radiator by a hose from the base of the radiator filler neck. The hot coolant level on all trucks should be at the FULL HOT mark on the expansion tank and the cold coolant level should be at the FULL COLD mark on the tank. Do not remove the radiator cap to check the coolant level.

roeoen( 7

85771104

Fig. 73 Gear oil is added through the filler plug bore, using a hand pump

Cooling System 85771066

FLUID RECOMMENDATIONS The proper coolant for your GM truck is a 50/50 mix of ethylene glycol antifreeze and water. Alcohol or methanol base ed, even in summer, to prevent rust and to take advantage of the solution’s higher boiling point compared to plain water. This is imperative on air conditioned trucks; the heater core can freeze if it isn’t protected.

Fig. 75 Coolant protection can be checked with a simple float type tester To check the coolant level: 1. Check the level on the see-through expansion tank.

«CAUTION The radiator coolant is under pressure when hot. To avoid the danger of physicai harm, coolant level should be

checked or replenished only when the engine is cold. 2. Check the level and, if necessary, add coolant to the proper level. Use a 50/50 mix of ethylene glycol antifreeze and

1-40

ROUTINE MAINTENANCE

85771068

Fig. 76 Check the radiator cap’s rubber gasket and metal seal for deterioration at least once a year

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85771108 85771069

Fig. 77 Remove any debris from the radiator’s cooling fins

Fig. 79 When adding a small amount of coolant to a system (not refilling the entire system), add coolant to the recovery tank only water. Alcohol or methanol base coolants are not recommended. Antifreeze solutions should be used, even in summer, to prevent rust and to take advantage of the solution’s higher boiling point compared to plain water. This is imperative on air conditioned trucks; the heater core can freeze if it isn’t protected. The coolant should be added through the coolant recovery tank, not the radiator filler neck.

CAUTION Never add large quantities of cold coolant to a hot engine. A cracked engine block may result. 3. Replace the cap. Each year the cooling system should be serviced as follows: e Wash the radiator cap and filler neck with clean water. e Check the coolant for proper level and freeze protection. e Have the system pressure tested (15 psi). If a replacement cap is installed, be sure that it conforms to the original specifications. e Tighten the hose clamps and inspect all hoses. Replace hoses that are swollen, cracked or otherwise deteriorated. e Clean the frontal area of the radiator core and the air conditioning condenser, if so equipped.

FLUSHING THE COOLING SYSTEM AND REFILLING 85771070

Fig. 78 For a warmed engine, coolant level should be above the COLD LEVEL line for this vehicle

The cooling system in your truck accumulates some internal rust and corrosion in its normal operation. A simple method of

ROUTINE MAINTENANCE REST

SIR SEBD PE

SPIER DOSS SSI GNP

PTFE SSUES ZA MS EP

keeping the system clean is known as flushing the system. It is performed by circulating a can of radiator flush through the system, draining the flush solution and refilling the system with the normal coolant. Radiator flush is marketed by several different manufacturers, and is available in cans or bottles at auto departments, parts stores, and many hardware stores. This operation should be performed every 30,000 miles or once a year. To flush the cooling system: 1. Drain the existing antifreeze and coolant. Open the radiator petcock and remove the engine drain plug (located near the bottom of the radiator and the bottom side of the engine block), or disconnect the bottom radiator hose at the radiator outlet. e>Before opening the radiator petcock, spray it with some penetrating oil. Be aware that if the engine has been run up to operating temperature, the coolant emptied will be HOT. 2. Close the petcock or reconnect the lower hose and fill the system with water; hot water if the system has just been run. 3. Add a can of quality radiator flush to the radiator or recovery tank, following any special instructions on the can. 4. Idle the engine as long as specified on the can of flush, or until the upper radiator hose gets hot. 5. Drain the system again. There should be quite a bit of scale and rust in the drained water. 6. Repeat this process until the drained water is mostly Clear. 7. Close all petcocks and connect all hoses. 8. Flush the coolant recovery reservoir with water and leave empty. 9. Determine the capacity of your truck’s cooling system (see Capacities specifications in this guide). Add a 50/50 mix of ethylene glycol antifreeze and water to provide the desired protection. 10. Run the engine to operating temperature, then stop the engine and check for leaks. Check the coolant level in the recovery tank and add, if necessary. 11. Check the protection level of your antifreeze mix with an antifreeze tester (a small, inexpensive syringe-type device available at any auto parts store). The tester has five or six small colored balls inside, each of which signify a certain temperature rating. Insert the tester in the recovery tank and suck just enough coolant into the syringe to float as many individual balls as you can (without sucking in too much coolant and floating all the balls at once). A table supplied with the tester will explain how many floating balls equal protection down to a certain temperature (three floating balls might mean the coolant will protect your engine down to 5 degrees F, for example). For problems with engine overheating, see Section 3.

‘Master Cylinder

:

SPE OSES BG OLE

SE Ng

PE SNEG

ESN

ES

SC

TS SRL

1-41 SE

HEE

the event of failure in either the front or rear brakes. The dual master cylinder has two entirely separate reservoirs, one connected to the front brakes and the other connected to the rear brakes. In the event of failure in either portion, the remaining

part is not affected. 1. Clean all of the dirt from around the cover of the master cylinder. 2. Be sure that the vehicle is resting on a level surface. 3. Carefully pry the clip from the top of the master cylinder to release the cover. Some late models have a plastic reservoir which do not have a clip. The plastic type caps can be removed by grasping the cap on both sides while pulling up on one side. Keep a rag handy just in case some fluid spills. Brake fluid will remove the paint finish so be careful. 4. The fluid level should be approximately ‘/ in. from the top of the master cylinder or, in the case of the plastic reservoir, above the minimum marks on reservoir sides. The fill marks on the plastic cylinders generally resemble a pair of steps embossed in the plastic. Be sure to use a high quality brake fluid such as General Motors Supreme No. 11 Hydraulic Brake Fluid, or fluids meeting DOT 3 specifications should be used. :

->Do not use brake fluid that has been used before or has been sitting in a container that has been open for a long period. Brake fluid will absorb moisture in an open or poorly sealed container. Contaminated brake fluid will greatly shorten the life of brake components. It is normal for the fluid level to fall slightly as the disc brake pads wear. However, if the level drops significantly between fluid level checks, or if the level is chronically low,

the system should be examined for leakage. 5. Install the cover of the master cylinder. On most models there is a rubber gasket under the cover, which fits into two slots on the cover. Be sure that this is seated properly. 6. Push the clip back into place and be sure that it seats in the groove on the top of the cover.

Brake fluid damages paint. It also absorbs moisture from the air; never leave a container or the master cylinder

uncovered any longer than necessary. All parts in contact with the brake fluid (i.e. master cylinder, and its lid, hoses, plunger assemblies, etc.) must be kept clean, since any

contamination of the brake fluid will adversely affect braking performance.

Power Steering Pump FLUID LEVEL CHECK » See Figures 83, 84, 85 and 86

BRAKE FLUID LEVEL CHECK

The power steering pump is belt driven; it is located at the front of the engine. The fluid level is checked at the reservoir,

» See Figures 80, 81 and 82 Chevrolet and GMC trucks are equipped with a dual braking system, that allows the truck to be brought to a safe stop in

RS

located on the top of the pump. The reservoir is part of the

1-42

ROUTINE MAINTENANCE

TILTED CYLINDER

LEVEL CYLINDER

85771072

wall top Fig. 80 If the master cylinder reservoir is not marked, make sure the fluid is within ‘/ in. reservoir

pew

“HOT”

MARK

“COLD”

MARK

85771110

Fig. 81 Some master cylinders are equipped with a plastic reservoir. Fluid must be kept above the min. lines, but ‘/ in. below the top

85771073

Fig. 83 Power steering reservoir dipstick markings

8

85771111

Fig. 82 Plastic reservoir lids are snapped into position and may be carefully pryed off by hand belt-driven power steering pump at the front of the engine. To

check the fluid level and/or add fluid: 1. Wipe off the cap and surrounding area, after stopping the engine with the wheels straight. 2. Remove the cap and attached dipstick. 3. Wipe the dipstick off with a clean, lint-free rag, replace the cap, and take a reading. If the fluid is hot, the level should be between HOT and COLD; if it is cold, it should be between COLD and ADD. 4. Either GM Power Steering Fluid or DEXRON@II Automatic Transmission Fluid may be used.

® 112

Fig. 84 The power steering pump is often located underneath other accessories such as the A/C compressor

Steering Gear The steering gear is factory filled with a lubricant which does not require seasonal change. The housing should not be drained; no lubrication is required for the life of the gear. The gear should be inspected for seal leakage when specified in the Maintenance Chart. Look for solid grease, not an oily film. If a seal is replaced or the gear overhauled, it should be filled with Part No. 1051052 which meets GM Specification GM 4673M, or its equivalent. Do not use EP Chassis Lube to

lubricate the gear and do not overfill.

ROUTINE MAINTENANCE

85771113

Fig. 85 Carefully reach down, unscrew and remove the pump reservoir cap

1-43

Jack up the front end of the truck and safely support it with jackstands. Block the rear wheels and firmly apply the parking brake. If the truck has been parked in temperatures below 20°F for any length of time, park it in a heated garage for an hour or so until the ball joints loosen up enough to accept the grease. Depending on which front wheel you work on first, turn the wheel and tire outward, either full-lock right or full-lock left. You now have the ends of the upper and lower suspension control arms in front of you; the grease nipples are visible pointing up (top ball joint) and down (lower ball joint) through the end of each control arm. If the nipples are not accessible enough, remove the wheel and tire. Wipe all dirt from the nipples or from around the plugs (if installed). If plugs are on the truck, remove them and install grease nipples in the holes (nipples are available in various thread sizes at most auto parts stores). Using a hand operated, low pressure grease gun loaded with a quality chassis grease, grease the ball joint only until the rubber joint boot begins to swell out.

STEERING LINKAGE » See Figure 88

85771114

Fig. 86 Check the appropriate markings on the cap dipstick

ECM

eC

ale]

The steering linkage should be greased at the same interval as the ball joints. Grease nipples are installed on the steering tie rod ends on most models. Wipe all dirt from around the nipples at each tie rod end. Using a hand operated, low pressure grease gun loaded with a suitable chassis grease, grease the linkage until the old grease begins to squeeze out around the tie rod ends. Wipe off the nipples and any excess grease. Also grease the nipples on the steering idler arms.

» See Figure 87 Water resistant EP chassis lubricant (grease) conforming to GM specification 6031-M should be used for all chassis grease points. Every year or 7,500 miles the front suspension ball joints, both upper and lower on each side of the truck, must be greased. Most trucks covered in this guide should be equipped with grease nipples on the ball joints, although some may have plugs which must be removed and nipples fitted.

PARKING BRAKE LINKAGE

Do not pump so much grease into the ball joint that excess grease squeezes out of the rubber boot. This destroys the watertight seal.

85771115

Fig. 87 There are various grease fittings located on the suspension, such as the control arm ball joints

1-44

ROUTINE MAINTENANCE

Use chassis grease on the parking brake cable where it contacts the cable guides, levers and linkage.

AUTOMATIC TRANSMISSION LINKAGE Apply a small amount of clean engine oil to the kickdown and shift linkage points at 7,500 mile intervals.

Body Lubrication HOOD LATCH AND HINGES Clean the latch surfaces and apply clean engine oil to the latch pilot bolts and the spring anchor. Also lubricate the hood hinges with engine oil. Use a chassis grease to lubricate all the pivot points in the latch release mechanism.

DOOR HINGES The gas tank filler door and truck doors should be wiped clean and lubricated with clean engine oil once a year. The door lock cylinders and latch mechanisms should be lubricated periodically with a few drops of graphite lock lubricant or a few shots of silicone spray.

Front Wheel Bearings

e Remove all outside dirt from the housing before exposing the bearing. e Treat a used bearing as gently as you would a new one. e Work with clean tools in clean surroundings. e Use clean, dry canvas gloves, or at least clean, dry hands, e Clean solvents and flushing fluids are a must. e Use clean paper when laying out the bearings to dry. e Protect disassembled bearings from rust and dirt. Cover them up. e Use clean rags to wipe bearings. @ Keep the bearings in oil-proof paper when they are to be stored or are not in use. e Clean the inside of the housing before replacing the bearing. Do NOT do the following: e Don’t work in dirty surroundings. e Don't use dirty, chipped or damaged tools. e Try not to work on wooden work benches or use wooden mallets. e Don’t handle bearings with dirty or moist hands. e Do not use gasoline for cleaning; use a safe solvent. e Do not spin-dry bearings with compressed air. They will be damaged. e Do not spin dirty bearings. e Avoid using cotton waste or dirty cloths to wipe bearings. e Try not to scratch or nick bearing surfaces. e Do not allow the bearing to come in contact with dirt or rust at any time. Four Wheel Drive

The procedure outlined below pertains to 2WD vehicles only. For bearing service procedures on 4WD vehicles, please refer to Section 7 in this manual.

Please refer to Section 7 for removal, installation, adjustment and repacking procedures.

REMOVAL PACKING AND INSTALLATION

1. Remove the wheel, tire assembly, and the brake drum or brake caliper. See Chapter 9 for details. 2. Remove the hub and disc as an assembly. Remove the caliper mounting bolts and insert a block between the brake pads as the caliper is removed. Remove the caliper and wire it up so its out of the way. 3. Clean, then pry off the grease cap, remove the cotter pin, spindle nut, and washer, and then remove the hub. Be careful that you do not drop the wheel bearings. 4. Remove the outer roller bearing assembly from the hub. The inner bearing assembly will remain in the hub and may be removed after prying out the inner seal. Discard this seal. 5. Clean all parts in solvent and allow to air dry. Check the parts for excessive wear or damage. 6. If the bearing cups are worn or scored, they must be replaced. Using a hammer and a drift, remove the bearing cups from the hub. When installing new cups, make sure that they are not cocked, and that they are fully seated against the hub shoulder. 7. Pack both wheel bearings using high melting point wheel bearing grease. Ordinary grease will melt, and ruin the pads. High temperature grease provides an extra margin of protection. Place a healthy glob of grease in the palm of one hand and force the edge of the bearing into it so that the grease fills the bearing. Do this until the whole bearing is packed. Grease packing tools are available to make this job a lot less

» See Figures 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106 and 107 Before handling the bearings, there are a few things that you should remember to do and not to do. Remember to DO the following:

85771116

Fig. 88 The steering linkage will also contain grease fittings

2-Wheel Drive

ROUTINE MAINTENANCE messy. There are also tools which make it possible to grease the inner bearing without removing it or the disc from the spindle. 8. Place the inner bearing in the hub and install a new inner seal, making sure that the seal flange faces the bearing cup. 9. Carefully install the wheel hub over the spindle. 10. Using your hands, firmly press the outer bearing into the hub. Install the spindle washer and nut. 11. To adjust the bearings on 1980 through 1984 models, spin the wheel hub by hand and tighten the nut until it is just snug (12 ft. lbs.). Back off the nut until it is loose, then tighten it finger tight. Loosen the nut until either hole in the spindle lines up with a slot in the nut, and insert a new cotter pin. There should be 0.001-0.005 in. end-play in the bearing. This can be measured with a dial indicator, if you wish. Replace the dust cap, wheel, and tire.

1-45

85771119

Fig. 91 After the ends of the cotter pin are straightened or cut, use a pair of wire cutters to pry the looped end free of the nut

85771120

85771117

Fig. 92 With the cotter pin removed, unscrew the castellated bearing nut

Fig. 89 Before removing the dust cap, a wire brush should be used to remove dirt or corrosion

85771121

85771118

Fig. 93 Once the nut is removed, the thrust washer may be carefully pryed free

Fig. 90 The dust cap may be loosened carefully using a prytool, then grasp the cap and remove it by hand

85771122

Fig. 94 While holding the rotor to keep it from falling, remove the outer wheel bearing

1-46

ROUTINE MAINTENANCE

85771123

Fig. 95 With the nut, washer and bearing removed, the

rotor can be removed from the spindle

Fig. 99 Be sure to thoroughly pack the inner and outer bearings using a suitable high temperature bearing grease

"85771129

Fig. 96 Use a small prybar to cock and remove the inner bearing seal from the rear of the rotor. Do not reuse the old seal.

Fig. 100 Install the inner bearing into the rear of the rotor. If the bearings are being reused, make sure the bearing is being installed in the same rotor as it was removed from.

85771125

Fig. 97 Remove the inner bearing from the rotor. If the bearings are to be reused, keep them separate as they must be installed in their original locations.

85771126

Fig. 98 If the bearings and races (bearing cups) are being reused, thoroughly clean the races of all old grease

85771130

Fig. 101 Install a new inner bearing seal. A suitably sized driver will assure proper installation.

85771131

Fig. 102 With the inner bearing and seal installed, the rotor may be positioned on the spindle. Be sure to grease the spindle before installation.

ROUTINE MAINTENANCE

1-47

85771132

Fig. 103 Hold the rotor in position on the spindle, then install the properly packed outer bearing

Fig. 106 Hand-tighten the spindle nut and install a new cotter pin

85771133

Fig. 104 Install the cleaned thrust washer over the outer bearing

85771136

Fig. 107 Install the dust cap using a small blunt punch to assure it is fully seated

85771134

Fig. 105 Install the outer bearing nut and tighten to 12 ft. Ibs. (16 Nm) while spinning the rotor. Once this is done, back the nut off to the just loose position.

TRAILER TOWING General Recommendations

:

It is important to remember that towing a trailer will place additional loads on your vehicle’s engine, drive train, steering, braking and other systems. However, if you find it necessary to tow a trailer, using the proper equipment is a must. Local laws may require specific equipment such as trailer brakes or fender mounted mirrors. Check your local laws.

Trailer Weight

:

The weight of the trailer is the most important factor. A good weight-to-horsepower ratio is about 35:1, 35 lbs. of GCW (Gross Combined Weight) for every horsepower your engine develops. Multiply the engine’s rated horsepower by 35 and subtract the weight of the truck passengers and cargo. The result is the approximate ideal maximum weight you should tow, although a a numerically higher axle ratio can help compensate for heavier weight.

1-48

ROUTINE MAINTENANCE

Figure the hitch weight to select a proper hitch. Hitch weight is usually 9-11% of the trailer gross weight and should be measured with the trailer loaded. Hitches fall into three types: those that mount on the frame and rear bumper or the bolt-on or weld-on distribution type used for larger trailers. Axle mounted or clamp-on bumper hitches should never be used. Check the gross weight rating of your trailer. Tongue weight is usually figured as 10% of gross trailer weight. Therefore, a trailer with a maximum gross weight of 2,000 Ib. will have a maximum tongue weight of 200 Ib. Class | trailers fall into this category. Class Il trailers are those with a gross weight rating of 2,000-3,500 Ib., while Class III trailers fall into the 3,500-6,000 Ib. category. Class IV trailers are those over 6,000 lb. and are for use with fifth wheel trucks, only. When you've determined the hitch that you'll need, follow the manufacturer's installation instructions, exactly, especially when it comes to fastener torques. The hitch will be subjected to a lot of stress and good hitches come with hardened bolts. Never substitute an inferior bolt for a hardened bolt.

Cooling Requirements ENGINE COOLING

t

I|

One of the most common, if not THE most common, problems associated with trailer towing is engine overheating. If you have a standard cooling system, without an expansion tank, you'll definitely need to get an aftermarket expansion tank kit, preferably one with at least a 2 quart capacity. These kits are easily installed on the radiator’s overflow hose, and come with a pressure cap designed for expansion tanks. Another helpful accessory is a Flex Fan. These fan are large diameter units are designed to provide more airflow at low speeds, with blades that have deeply cupped surfaces. The blades then flex, or flatten out, at high speed, when less cooling air is needed. These fans are far lighter in weight than stock fans, requiring less horsepower to drive them. Also, they are far quieter than stock fans. If you do decide to replace your stock fan with a flex fan, note that if your car has a fan clutch, a spacer between the flex fan and water pump hub will be needed. Aftermarket engine oil coolers are helpful for prolonging engine oil life and reducing overall engine temperatures. Both of these factors increase engine life.

PUSHING AND TOWING Push Starting Chevrolet and GMC trucks with manual transmissions can be push started. To push start, make sure that both bumpers are in reasonable alignment. Turn the ignition key to ON and engage High

While not absolutely necessary in towing Class | and some Class II trailers, they are recommended for heavier Class I and all Class III towing. on Engine oil cooler systems consist of an adapter, screwed in place of the oil filter, a remote filter mounting and a multitube, finned heat exchanger, which is mounted in front of the radiator or air conditioning condenser.

TRANSMISSION COOLING An automatic transmission is usually recommended for trailer towing. Modern automatics have proven reliable and, of course, easy to operate, in trailer towing. The increased load of a trailer, however, causes an increase in the temperature of the automatic transmission fluid. Heat is the worst enemy of an automatic transmission. As the temperature of the fluid increases, the life of the fluid decreases. In order to reduce transmission fluid temperature, it is recommended that you install an automatic transmission cooler. The cooler, which consists of a multi-tube, finned heat exchanger, is usually installed in front of the radiator or air conditioning compressor, and hooked in-line with the transmission cooler tank inlet line. Follow the cooler manufacturer's installation instructions. Select a cooler of at least adequate capacity, based upon the combined gross weights of the truck and trailer. Cooler manufacturers recommend that you use an aftermarket cooler in addition to, and not instead of, the present cooling tank in your radiator. If you do want to use it in place of the radiator cooling tank, get a cooler at least two sizes larger than normally necessary. ->A transmission cooler can sometimes cause slow or harsh shifting in the transmission during cold weather, until the fluid has a chance to come up to normal operating temperature. Some coolers can be purchased with or retrofitted with a temperature bypass valve which will allow fluid flow through the cooler only when the fluid has reached operating temperature, or above.

Handling A Trailer Towing a trailer with ease and safety requires a certain amount of experience. It’s a good idea to learn the feel of a trailer by practicing turning, stopping and backing in an open area such as an empty parking lot.

|

|

gear. Depress the clutch pedal. When a speed of about 10 mph is reached, slightly depress the gas pedal and slowly release the clutch. The engine should start. Automatic transmission equipped trucks cannot be started by push starting.

ROUTINE MAINTENANCE

1-49

properly, or when speeds of over 35 mph will be used or when towing more than 50 miles.

«i CAUTION

TWO WHEEL DRIVE

If a truck is towed on its front wheels only, the steering wheel must be secured with the wheels in a straight ahead position.

Chevrolet and GMC trucks can be towed on all four wheels (flat towed) at speeds of less than 35 mph for distances less than 50 miles, providing that the axle, driveline and engine/transmission are operable. The transmission should be in Neutral, the engine should be off, the steering column unlocked, and the parking brake released. Do not attach chains to the bumpers or bracketing. All attachments must be made to the structural members. Safety chains should be used. It should also be remembered that power steering and brake assists will not be working with the engine off. The rear wheels must be raised off the ground or the driveshaft disconnected when the transmission is not operating

FOUR WHEEL DRIVE Details for towing procedures are given in the Towing Four Wheel Drive Chart. Remember that the power steering and power brakes will not have their power assist with the engine off. The only safe way to tow is with a tow bar. The steering column must be unlocked and the parking brake released. Attachments should be made to the frame and to the bumper or its brackets.

Safety chains are also required. e>When towing a full time four wheel drive manual transmission truck with all four wheels on the ground, the transfer case must be in Neutral and the transmission in

high gear. There is no speed restriction.

Four Wheel Drive Towing Chart FRONT WHEELS OFF FULL TIME ( 4 X 4) AUTOMATIC TRANSMISSION 1. TRANSFER CASE IN NEUTRAL 2. TRANSMISSION IN PARK 3. MAXIMUM SPEED 35 MPH 4. MAXIMUM DISTANCE 50 MILES

1. 2. 3. 4. NOTE: For distances over 50 miles, disconnect rear propshaft at rear axle carrier and secure in safe position.

PART TIME (4 X 4) MANUAL TRANSMISSION TRANSFER CASE IN 2H TRANSMISSION IN NEUTRAL MAXIMUM SPEED 35 MPH MAXIMUM DISTANCE 50 MILES

NOTE: For distances over 50 miles, disconnect at rear axle carrier and secure in safe position.

REAR WHEELS CAUTION:

THE GROUND

O

H

the rear propshaft

ROUND

When towing a vehicle in this position, the steering wheel should be secured to k:eep the front wheels

in a straight ahead position.

1. TRANSFER CASE IN NEUTRAL 2. TRANSMISSION IN PARK 3. MAXIMUM SPEED 35 MPH 4. MAXIMUM DISTANCE 50 MILES NOTE: For distances over 50 miles, disconnect front propshaft at

1. TRANSFER CASE IN 2H 2. TRANSMISSION IN NEUTRAL 3. MAXIMUM SPEED 35 MPH 4. MAXIMUM DISTANCE 50 MILES NOTE: For distances over 50 miles, disconnect the front propshaft

front axle carrier and secure in safe position.

at front axle carrier and secure in safe position.

a

POOR

ALL

Red) ross

FOUR

WHEELS

eee

1. TRANSFER CASE IN NEUTRAL 2. TRANSMISSION IN PARK NOTE: Do not exceed speed as per State laws for towing vehicles.

ON GROUND

PART TIME

(4X 4

1. TRANSFER CASE IN 2H 2. TRANSMISSION IN NEUTRAL 3. MAXIMUM SPEED 35 MPH 1. MAXIMUM DISTANCE 50 MILES NOTE: For speeds or distances greater than above, both propshafts must be disconnected at the axle carrier end and secured in a safe position. It is recommended that both propshafts be removed and stored in the vehicle. NOTE: Do not exceed

; speeds as per State laws for towing vehicles. 85771074

1-50

ROUTINE MAINTENANCE

» See Figures 108 and 109

2k CAUTION To reduce the risk of personal injury, follow all jacking and stowage instructions. Use the jack only for lifting the vehicle during wheel change. Never get beneath the vehicle, start or run the engine while the vehicle is supported by the jack. Always secure and stow spare or flat tire and all jacking equipment. 1. Park on a level surface and firmly set parking brake.

85771075

Fig. 108 Rear jacking point

85771137

Fig. 109 The same points of the frame which can be used on a hoist to support the vehicle, may also be used to support the vehicle using jackstands 2. Turn on hazard warning flasher, if necessary. 3. Set automatic transmission in PARK (manual transmission in REVERSE). 4. Block front and rear of tire at corner diagonally opposite to one being raised. 5. Remove jacking tools from stowage area. 6. Raise jack until lift head engages lower control arm (front location 2 wheel drive) or axle (front location 4wheel drive/rear location 2 or 4 wheel drive). 7. Raise vehicle by rotating jack handle clockwise. 8. Make sure vehicle is supported properly, with jackstands before starting any repairs.

ROUT! NE MAINTENANCE

1-51

CAPACITIES Engine Displacement (cu.in.)

250 292

Engine Crankcase Transmission ts. ts. With Without Manual Auto Filter Filter + 3-spd 4-spd (Refill)

4 5 4

6

Drive Axle Front Rear

[320/80 | © | 5@ 80 | © | 50 5@ 5®

Fuel ‘Transfer Tank Case (gals.) (pts.)

| © | 200 wae | © |20@ | 50 | © |20@ | 50

— |© |2@]}] 5@ | © |2@ | 50

| 5@ | © | 2@|

5 | © | 20@ paea we meso 350

Sor

5 |© 5 |©

4. |

4

454

6

3

8

m oe [ets stele

pee

305 5s

6

|2@] [2]

50 5 5

Cooling System ts. w/oA/C w/A/C

17:60)

poet

eel

Po

15.0 14.8 18.0 |418,0 iatene

18.0 Pee 20.4 |20.4 | 20.4

24.4@| 24.7 |24.7

15.0 15.0

17.5 17.6) ol17,Senuhee

19.0 | 20.0

5

23.0 | 24.0

[stets

Bs

be) 4 | 38 Pe | © | 6 | Oe | © | ei

Oe

HD

cee

ies OMS 5 |©

17.5 _|17.5 17.5 | 17.5

moi |7 | - |s [elo |stole| so |os |ms lms ahs | 1 | 6 | 3 8) © | 5 | |e ses Poe 1985-86

250 | 5 mem SWS. Eo Oe

305 5 350 7 Diesel | 7

4 6

7ee a

| | 8 3. [| 8. Siar 3 8 3 |8

o | oy 6 | °| sen ais © |© 5@ © | @ | 5@ 5 |o | @ | 50

5

175. 23.0 25.0

10.9 |10.9 14.0 | 14.0 eae

|180m

_ =

24.0 85771076

ROUTINE MAINTENANCE

1-52

CAPACITIES

Year

PORTER

Engine ais Transmission Crankcase (pts.) (qts.) Auto Manual With Without (Refill) 4-spd Filter © 3-spd Filter

Engine Displacement (cu. in.)

e| OER

||

5

3

Drive Axle Rear Front

Transfer Fuel Case Tank (pts.) (gals.)

Cooling System ts. w/A/C w/oA/C

—

HD

ae ag a

305 350 454

Diesel © Heavy-duty 3-speed—3.5 pts. © Powerglide—4.0 pts. Turbo Hydra-Matic 350—5.0 pts. Turbo Hydra-Matic 400—7.5 pts. ® 3,300 and 3,500 Ib. Chevrolet axles—4.5 pts. 5,200 and 7,200 Ib. Chevrolet axles—6.5 pts. 5,500 Ib. Dana axles—6.0 pts. 11,000 Ib. Chevrolet axles—14.0 pts.

® 20 Series—21.0 gals. © Full-time 4WD—8 pts. © 81/2 in. ring gear—4.2 pts. 87/s in. ring gear (Chevrolet)—4.5 pts. (3.5 pts. (1980-82) 93/s in. ring gear (Dana)—6.0 pts. 101/2 in. ring gear (Chevrolet)—61/2 pts. 101/2 in. ring gear (Dana)—7.2 pts. 121/2 in. ring gear (Chevrolet)— 26.8 pts.

© Tremec 3-spd—4.0 pts. Muncie 3-spd—3.0 pts.

81/2 in. ring gear—4.25 pts. (1980)

® 10 pts. on 208 transfer cases ® Short bed w/single tank: 16 gal., 32 gal. w/dual tanks

Long bed w/single tank: 20 gal. Long bed w/dual tanks under 8600 GVWR 32 gal. Long bed w/dual tanks over 8600 GVWR 40 gal. All diesel w/dual tanks 40 gal.

Turbo Hydra-Matic 350—6 pts, Turbo Hydra-Matic 400—7 pts. 1985 only 9 pts. Turbo Hydra-Matic 700R4—10 pts.

® K10-20: 2 Quarts, K30: 3 Quarts Oil Filter should be changed at EVERY OIL CHANGE

® V15/10, V25/20—5.2 ats. V35/30—3.0 ats.

Suburban, Gas: 25 gal. Diesel: 27 gal. Pick-up, Shortbed—16 gal. Longbed—20 gal.

V15/10, V25/20—10.4 pts. V35/30—5.0 pts.

® 22.8—1980

16.0 gal.—short wheelbase models ® Not used 8577107C

ROUTINE MAINTENANCE — 1-53 SS

SRY

I

ATI

TL

TS

STS

NTS

TA

IIE

SU

SDR

TR GSU

TTS

ST

SUS

EST

TS

MAINTENANCE INTERVALS Maintenance

Interval

Air Cleaner (Check and Clean) Paper element ©

30,000 mi. (replace)©

PCV Valve (Replace)

12 mo./15,000 mi@

Evaporative Canister Replace filter

24 mo./30,000 mi.©

Engine Oil Check Replace Engine Oil Filter (Replace)

Each fuel stop 6 mo./7,500 mi. © ® At 1st oil change; then every 2nd®

Fuel Filter

Replace©

Turbo Hydra-Matic Fluid & Filter Check fluid Change fluid Replace filter Manual transmission (All) Check lubricant Add lubricant Change lubricant Battery Lubricate terminal felt washer Clean terminals Check electrolyte level Coolant Level Front Wheel Bearings Lubricate Front and Rear Axle Lube Check Replace standard axle Replace locking axle Brake Fluid (Master Cylinder) Check fluid level Add fluid Manual Steering Gear Lubricant Check level Add lubricant Power Steering Reservoir Check fluid level Add fluid

12 mo./15,000 mi. © ® Each oil change 30,000 mi. 30,000©

6 mo./7,500 mi. © As necessary

As necessary Twice monthly

Each fuel stop

30,000 mi. © ©

7,500 mi. @®@

1st 6,000 mi. © © 6 mo./7,500 mi. © As necessary

30,000 mi. @ 6 mo./7,500 mi. As necessary

Rotate Tires

Radial—1st 7,500 mi., then every 15,000 mi. Bias Belted—every 7,500 mi.

Chassis Lubrication

See Chassis Lubrication charts

Drive Belts

Check and adjust (as necessary) Transfer Case Check Add

6 mo./7,500 mi.

4 mo./6,000 mi. As necessary 85771077

1-54

ROUTINE MAINTENANCE

ee

MAINTENANCE INTERVALS Maintenance

Interval

Driveshaft Centering Ball Lubricate (4WD only)

. 7,500 mi. ©

NOTE: Heavy-duty operation (trailer towing, prolonged idling, severe stop-and-start driving) should be accompanied by a 50% increase in maintenance. Cut the interval in half for these conditions. Figures given are maintenance intervals when service should be performed. —Not applicable mi.—Miles mo.—Months @ Paper element air cleaners should be rotated 180° each time they are checked. ® From 1980 on, no lubrication of the manual steering gear is recommended. The gear should be inspected for leaks at the seal (lubricant leaks, not filmy oil leaks). Seasonal change of the lubricant is not required and the housing should not be drained. ® Change at 24,000 mi. for trucks over 8600 GVW

@ Change at 6,500 mi. for trailer towing or severe service

© Change at 10,000 mi. for trucks over 8600 GVW © 12,000 mi. in heavy duty emissions vehicles (C 10 or C-1500 over 6000 Ibs. GVW; all K models) ® 24 mo./30,000 mi. 1980-87

24,000 mi. in heavy duty emission vehicles ® 4 mo. 6,000 mi. in heavy duty emissions vehicles 100,000 mi. 1979-86 light duty emissions vehicles.

® 12,000 mi. in four wheel drive vehicles @® Change at 7,500 mi. then every 30,000 mi. on 1986-87 with 4 speed (RPO M73) ® Change at 3,000 mile intervals for 350 Diesel; 6,000 miles for 1981 and later models Change at 5,000 mile intervals for 379 (6.2L) Diesel; or every 2,500 miles when operating under extreme temperatures, extended high speed or idle conditions, or frequent trailer towing.

® Figures include diesel fuel filters. 85771078

IDLE SPEED AND MIXTURE ADJUSTMENTS CARBURETED ENGINES 2-20 DIESEL ENGINE 2-25 THROTTLE BODY INJECTION (TBI) ENGINES 2-25 DIESEL INJECTION TIMING INJECTION PUMP TIMING 2-19 ELECTRONIC IGNITION COMPONENT REPLACEMENT 2-14 HIGH ENERGY IGNITION (HEl) SYSTEM 2-11 TROUBLESHOOTING THE HEI SYSTEM 2-12 FIRING ORDERS 2-10 IGNITION TIMING INSPECTION AND ADJUSTMENT 2-18 TIMING 2-18 SPECIFICATIONS CHARTS DIESEL TUNE-UP SPECIFICATIONS 2-6 GASOLINE ENGINE TUNE-UP SPECIFICATIONS 2-5 TROUBLESHOOTING ENGINE PERFORMANCE 2-7 TUNE-UP PROCEDURES SPARK PLUG WIRES 2-4 SPARK PLUGS 2-2 VALVE LASH 2-20

~ENGINE PERFORMANCE AND TUNE-UP IDLE SPEED AND MIXTURE ADJUSTMENTS 2-20 DIESEL INJECTION TIMING 2-19 ELECTRONIC IGNITION 2-11 al iatlN(C@) 519)=|ntolaral10) IGNITION TIMING’ 2-18 SPECIFICATIONS CHARTS 2-5 - TUNE-UP PROCEDURES 2-2 VALVE LASH 2-20

2-2

ENGINE PERFORMANCE AND TUNE-UP

TE

TUNE-UP PROCEDURES In order to extract the full measure of performance and economy from your engine it is'essential that it be properly tuned at regular intervals. A regular tune-up will keep your vehicle’s engine running smoothly and will prevent the annoying minor breakdowns and poor performance associated with an untuned engine. Neither tune-up nor troubleshooting can be considered, independently since each has a direct relationship with each other. It is advisable to follow a definite and thorough tune-up procedure. Tune-up consists of three separate steps: 1. Determine whether normal wear is responsible for performance loss. 2. Determine what parts require replacement service. 3. Installation and adjustment of new or existing parts. The manufacturer's recommended interval for tune-ups is 22,500 miles or 18 months, except for heavy duty emission models, which use the 12 months or 12,000 mile schedule in all years. These intervals should be shortened if the truck is subjected to severe operating conditions such as trailer pulling, off-road driving, or if starting and running problems are noticed. It is assumed that the routine maintenance described in Section 1 has been kept up, as this will have an effect on the results of the tune-up. All the applicable tune-up steps should — be followed, as each adjustment complements the effects of the others. If the emission control sticker in the engine compartment disagrees with the information presented in the Tune-up Specifications chart in this section, the sticker figures must be followed. The sticker information reflects running changes made by the manufacturer during production. The light duty sticker is usually found on the underhood sheet metal above the grille. The heavy duty sticker is usually on top of the air cleaner. Diesel engines do not require tune-ups, as there is no ignition system. Troubleshooting is a logical sequence of procedures designed to locate a particular cause of trouble. Troubleshooting Charts in this book can be found at the end of each section where applicable and are general in nature (applicable to most vehicles), yet specific enough to locate the problem. It is advisable to read the entire section before beginning a tune-up, although those who are more familiar with tune-up procedures may wish to go directly to the instructions.

| current can arc. The ignition coil produces anywhere from 20,000 to 40,000 volts which travels to the distributor where it is distributed through the spark plug wires to the spark plugs. The current passes along the center electrode and jumps the gap to the side electrode, and, in do doing, ignites the air/fuel mixture in the combustion chamber. Rough idle, hard starting, frequent engine miss at high speeds and physical deterioration are all indications that the plugs should be replaced. The electrode end of a spark plug is a good indicator of the internal condition of your engine. If a spark plug is fouled, ° causing the engine to misfire, the problem will have to be found and corrected. Often, reading the plugs will lead you to the cause of the problem. eA small amount of light tan or rust red colored deposits at the electrode end of the plug is normal. These plugs need not be renewed unless they are severely worn.

SPARK PLUG HEAT RANGE » See Figure 3 Spark plug heat range is the ability of the plug to dissipate heat. The longer the insulator the hotter the plug will operate; the shorter the insulator the cooler it will operate. A plug that absorbs little heat and remains too cool will quickly accumulate deposits of oil and carbon since it is not hot enough to burn

PORCELAIN

~— INSULATOR INSULATOR CRACKS OFTEN OCCUR HERE

ae

Spark Plugs » See Figures 1 and 2 A typical spark plug consists of a metal shell surrounding a ceramic insulator. A metal electrode extends downward through the center of the insulator and protrudes a small distance. Located at the end of the plug and attached to the side of the outer metal shell is the side electrode. The side electrode bends in at a 90° angle’so that its tip is even with, and parallel to, the tip of the center electrode. The distance between these two electrodes (measured in thousandths of an inch) is called the spark plug gap. The spark plug in no way produces a spark but merely provides a gap across which the

(PROPER GAP)

CENTER ELECTRODE FALE FLAT WHEN ADJUSTING GAP— DO NOT BEND!

SIDE ELECTRODE (BEND TO ADJUST GAP) 85772002

Fig. 1 Spark plug cutaway

ENGINE PERFORMANCE AND TUNE-UP

2-3

REPLACING SPARK PLUGS » See Figures 4, 5, 6 and 7

A set of spark plugs usually requires replacement after about 20,000 to 30,000 miles, depending on your style of driving. In normal operation, plug gap increases about 0.001 inch for every 1,000-2,500 miles. As the gap increases, the plug’s voltage requirement also increases. It requires a greater voltage to jump the wider gap and about two to three times as much voltage to fire a plug at high speeds than at idle. When you're removing spark plugs, you should work on one at a time. Don’t start by removing the plug wires all at once, because unless you number them, they may become mixed up. Take a minute before you begin and number the wires with tape. The best location for numbering is near where the wires come out of the cap.

GASKET NOT USED

REMOVAL & INSTALLATION

~—=—__

TAPERED

SEAT 857720a4

Fig. 2 The 5/8 spark plug does not require a gasket. Sealing is accomplished by the tapered seat on the plug. them off. This causes a plug to foul and consequently, to misfire. A plug that absorbs too much heat will have no deposits, but, due to the excessive heat, the electrodes will burn away quickly and in some instances, pre-ignition may result. Pre-ignition takes place when plug tips get so hot that they glow sufficiently to ignite the fuel/air mixture before the actual spark occurs. This early ignition will usually cause a pinging during low speeds and heavy loads. The general rule of thumb for choosing the correct heat range when picking a spark plug is to use the same type as the original plugs but if most of your driving is long distance, high speed travel, use a colder plug; if most of your driving is stop and go, use a hotter plug.

1. Before removing the spark plugs, number the plug wires so that the correct wire goes on the plug when replaced. This can be done with pieces of adhesive tape. 2. Next, clean the area around the plugs by brushing or blowing with compressed air. 3. Disconnect the plug wires by twisting and pulling on the rubber cap, not on the wire. On High Energy Ignition (H.E.I.) systems, twist the plug caps ‘/2 turn in either direction to break

Fig. 4 These tools are commonly required to replacement of the spark plugs.

vex\l

EON IELTS POEL Caern=

™eee Swy vasaa

a

‘a T 85772001

Fig. 3 Spark plug heat range showing different electrode lengths. Colder plug (shorter electrode) is on left

851772003

Fig. 5 Pull on the spark plug boot, not on the wire

2-4

ENGINE PERFORMANCE AND TUNE-UP require removing the cylinder head to reach the broken piece, and could also result in cylinder wall, piston ring, or valve damage.

Never bend the center electrode of the spark plug. This will break the insulator.

85772005

Fig. 6 Gap the plug with a wire gauge; a flat gauge will give and inaccurate reading

7. Clean the plug threads with a wire brush. Lubricate the threads with a drop of oil. 8. Screw the plugs in finger tight, and then tighten them with the spark plug socket. Be very careful not to overtighten them. If a torque wrench is available, torque them to 15 ft. Ibs. for plug designations with a T, 25 ft. Ibs. for all the rest. 9. Reinstall the wires. If, by chance, you have forgotten to

number the plug wires, refer to the Firing Order illustrations in this Section.

SPARK PLUG WIRES » See Figures 8 and 9

85772006

Fig. 7 Bend the side electrode to adjust the gap. Never bend the center

we

’Es? e

r ea | 5 aes Wee aRPE

Res ar) 5 Isseor REla

is | |

the seal before removing the wire. Never remove the wires from H.E.|. systems when the engine is running. Severe shock could result. 4. Remove each plug with a rubber insert spark plug socket. Make sure that the socket is all the way down on the plug to prevent it from slipping and cracking the porcelain insulator. On some V8s the plugs are more accessible from under the truck. 5. After removing each plug, evaluate its condition. If the electrode shows signs of wear, replace the spark plug. Use the plug recommended by the factory. The letter codes on the General Motors original equipment type plugs are read this way: e R resistor

e S extended tip

e T tapered seat e X wide gap The numbers indicate heat range; hotter running plugs have higher numbers. 6. If the plugs are to be reused, file the center and side

electrodes flat with a fine, flat points file. Heavy or baked on | deposits can be carefully scraped off with a small knife blade or the scraper tool on a combination spark plug tool. Check the gap between the electrodes with a round wire spark plug gapping gauge. Do not use a flat feeler gauge; it will give an inaccurate reading. If the gap is not as specified, use the bending tool on the spark plug gap gauge to bend the outside electrode. Be careful not to bend the electrode too far or too . often, because excessive bending may cause the electrode to . break off and fall into the combustion chamber. This would

_=

Visually inspect the spark plug cables for burns, cuts, or breaks in the insulation. Check the spark plug boots and the nipples on the distributor cap and coil. Replace any damaged wiring. If no physical damage is obvious, the wires can be checked with an ohmmeter for excessive resistance. When installing a new set of spark plug cables, replace the cables one at a time so there will be no mix-up. Start by replacing the longest cable first. Install the boot firmly over the spark plug. Route the wire exactly the same as the original.

Fig. 8 Most HEI equipped engines covered ual should be equipped with a spark plug harness that snaps to the top of the wires tributor cap. As in the case of this photo, uncommon to find these missing.

in this manwire retainer on the disit is not

ENGINE PERFORMANCE AND TUNE-UP

2-7

Troubleshooting Engine Performance Problem

Hard starting (engine cranks normally)

Cause

Solution

> Binding linkage, choke valve or choke piston

- Repair as necessary

* Restricted choke vacuum

- Clean passages

diaphragm * Improper fuel level

- Dirty, worn or faulty needle valve

* Adjust float level - Repair as necessary

and seat

* * *

Float sticking Faulty fuel pump Incorrect choke cover adjustment Inadequate choke unloader adjustment Faulty ignition coil Improper spark plug gap Incorrect ignition timing Incorrect valve timing

* *

»

Repair as necessary Replace fuel pump Adjust choke cover Adjust choke unloader

- Test and replace as necessary - Adjust gap

- Adjust timing * Check valve timing; repair as

necessary Rough idle or stalling

* Incorrect curb or fast idle speed - Incorrect ignition timing * Improper feedback system operation + Improper fast idle cam adjustment - Faulty EGR valve operation

* Adjust curb or fast idle speed * Adjust timing to specification - Refer to Chapter 4

- Faulty PCV valve air flow

- Test PCV valve and replace as

- Choke binding

- Locate and eliminate binding con-

* Faulty TAC vacuum motor or valve

> Repair as necessary

> Air leak into manifold vacuum

+ Improper fuel level + Faulty distributor rotor or cap + Improperly seated valves

* Inspect manifold vacuum connections and repair as necessary - Adjust fuel level * Replace rotor or cap * Test cylinder compression, repair

* Incorrect ignition wiring

* Inspect wiring and correct as

- Faulty ignition coil

- Test coil and replace as necessary

Restricted air vent or idle passages * Restricted air cleaner

- Clean passages

- Faulty choke vacuum diaphragm

- Repair as necessary

- Restricted idle transfer slots - Restricted idle air vents and

* Clean transfer slots

+ Adjust fast idle cam i * Test EGR system and replace as

necessary necessary

dition

as necessary necessary e

* Clean or replace air cleaner filler element

Faulty low-speed operation

- Clean air vents and passages

passages - Restricted air cleaner

- Clean or replace air cleaner filter

> Improper fuel level - Faulty spark plugs

+ Adjust fuel level * Clean or replace spark plugs

element

85772C01

9-8

ENGINE PERFORMANCE AND TUNE-UP

Troubleshooting Engine Performance a Cause Problem

Faulty low-speed operation (cont.)

Faulty acceleration

Solution

- Dirty, corroded, or loose ignition secondary circuit wire connections - Improper feedback system operation - Faulty ignition coil high voltage wire - Faulty distributor cap

- Clean or tighten secondary circuit

+ Improper accelerator pump stroke * Incorrect ignition timing - Inoperative pump discharge check ball or needle - Worn or damaged pump diaphragm or piston - Leaking carburetor main body cover gasket * Engine cold and choke set too lean * Improper metering rod adjustment

- Adjust accelerator pump stroke - Adjust timing - Clean or replace as necessary

wire connections

- Refer to Chapter 4 - Replace ignition coil high voltage wire

+ Replace cap

* Replace diaphragm or piston

- Replace gasket - Adjust choke cover

+ Adjust metering rod

* Faulty spark plug(s) - Improperly seated valves

+ Clean or replace spark plug(s) + Test cylinder compression, repair

* Faulty ignition coil * Improper feedback system

- Test coil and replace as necessary - Refer to Chapter 4

as necessary

operation

Faulty high speed operation

* Incorrect ignition timing - Faulty distributor centrifugal advance mechanism

- Adjust timing - Check centrifugal advance mechanism and repair as necessary

» Faulty distributor vacuum advance mechanism - Low fuel pump volume - Wrong spark plug air gap or wrong plug » Faulty choke operation - Partially restricted exhaust manifold, exhaust pipe, catalytic converter, muffler, or tailpipe » Restricted vacuum passages * Improper size or restricted main jet - Restricted air cleaner

« Check vacuum advance mechanism and repair as necessary

* Faulty distributor rotor or cap * Faulty ignition coil * Improperly seated valve(s)

* Replace rotor or cap * Test coil and replace as necessary * Test cylinder compression, repair

» Faulty valve spring(s)

- Inspect and test valve spring tension, replace as necessary * Check valve timing and repair as

- Replace fuel pump » Adjust air gap or install correct plug. - Adjust choke cover * Eliminate restriction

- Clean passages * Clean or replace as necessary * Clean or replace filter element as

necessary

as necessary * Incorrect valve timing

necessary 85772C02

ENGINE PERFORMANCE AND TUNE-UP

2-9

Troubleshooting Engine Performance (cont.) Problem

Faulty high speed operation (cont.)

Cause

Solution

* Intake manifold restricted

- Remove restriction or replace

+ Worn distributor shaft - Improper feedback system

- Replace shaft - Refer to Chapter 4

manifold

operation

Misfire at all speeds

* + -

Faulty spark plug(s) Faulty spark plug wire(s) Faulty distributor cap or rotor Faulty ignition coil Primary ignition circuit shorted or open intermittently - Improperly seated valve(s)

* Clean or replace spark plug(s) * Replace as necessary

- Faulty hydraulic tappet(s) - Improper feedback system operation + Faulty valve spring(s)

- Clean or replace tappet(s) - Refer to Chapter 4

+ Replace cap or rotor - Test coil and replace as necessary * Troubleshoot primary circuit and repair aS necessary * Test cylinder compression, repair as necessary

- Worn camshaft lobes * Air leak into manifold

- Inspect and test valve spring tension, repair as necessary - Replace camshaft * Check manifold vacuum and repair

+ -

+ * -

as necessary

Improper carburetor adjustment Fuel pump volume or pressure low Blown cylinder head gasket Intake or exhaust manifold passage(s) restricted - Incorrect trigger wheel installed in

Adjust carburetor Replace fuel pump Replace gasket Pass chain through passage(s) and repair as necessary - Install correct trigger wheel

distributor

Power not up to normal

* * + * *

Incorrect ignition timing Faulty distributor rotor Trigger wheel loose on shaft Incorrect spark plug gap Faulty fuel pump Incorrect valve timing

+ * *

Adjust timing Replace rotor Reposition or replace trigger wheel Adjust gap Replace fuel pump Check valve timing and repair as

necessary - Faulty ignition coil * Faulty ignition wires

* Test coil and replace as necessary - Test wires and replace as neces-

+ Improperly seated valves

* Test cylinder compression and repair as necessary - Replace gasket - Test compression and repair as

sary - Blown cylinder head gasket * Leaking piston rings

necessary

Intake backfire

- Worn distributor shaft * Improper feedback system operation

- Replace shaft + Refer to Chapter 4

+ » -

- Adjust timing

Improper ignition timing Faulty accelerator pump discharge Defective EGR CTO valve Defective TAC vacuum motor or valve

S

- Repair as necessary - Replace EGR CTO valve - Repair as necessary 85772003

2-10 ENGINE PERFORMANCE AND TUNE-UP _ Troubleshooting Engine Performance (cont.) - Check float level or manifold

- Lean air/fuel mixture

Intake backfire (cont.)

Exhaust backfire

Solution

Cause

Problem

vacuum for air leak. Remove sediment from bowl

» Air leak into manifold vacuum

;

- Faulty air injection diverter valve

- Exhaust leak Ping or spark knock

: Incorrect ignition timing - Distributor centrifugal or vacuum advance malfunction - Excessive combustion chamber deposits : Air leak into manifold vacuum - Excessively high compression

i

Hh. Surging (at cruising to top speeds)

“i

- Fuel octane rating excessively low * Sharp edges in combustion chamber - EGR valve not functioning properly

- Low carburetor fuel level * Low fuel pump pressure or volume + Metering rod(s) not adjusted properly * Improper PCV valve air flow ae dias

- ‘Air leak into manifold vacuum

* Check manifold vacuum and repair as necessary - Test diverter valve and replace as necessary * Locate and eliminate leak + Adjust timing + Inspect advance mechanism and repair as necessary - Remove with combustion chamber — cleaner + Check manifold vacuum and repair as necessary + Test compression and repair as necessary - Try alternate fuel source - Grind smooth - Test EGR system and replace as necessary , + Adjust fuel level _: Replace fuel pump * Adjust metering rod

- Test PCV valve and replace as necessary * Check manifold vacuum and repair

Se., * * =

“1

Incorrect spark aval Restricted main jet(s) « ” Undersize main jet(s) Restricted air vents Restricted fuel filter

as necessary * + * . -

Test and replace as necessary Clean main jet(s) Replace main jet(s) Clean air vents Replace fuel filter

* Restricted air cleaner

* Clean or replace air cleaner filter element

- EGR valve not functioning properly

+ Test EGR system and replace as necessary » Refer to Chapter 4 c

* Improper feedback system operation

85772CA3

[

FIRING ORDERS » See Figures 10, 11 and 12 -*To avoid confusion, remove and tag the wires one at a

time, for replacement.

=

ENGINE PERFORMANCE AND TUNE-UP

2-11

FIRING ORDER 1-8-4-3-6-5-7-2

85772007

Fig. 10 6 cylinder engine Engine firing order: 1-5-3-6-2-4 Distributor rotation: Clockwise

85772009

Fig. 12 V8 engine Engine firing order: 1-8-4-3-6-5-7-2 Distributor rotation: Clockwise

ENGINE FIRING ORDER: 16-54-32 DISTRIBUTOR ROTATION: CLOCKWISE

85772008

Fig. 11 V6-262 engine Engine firing order: 1-6-5-4-3-2 Distributor rotation: Clockwise

ELECTRONIC IGNITION

High Energy Ignition (HEI) System » See Figure 13

r

The General Motors High Energy Ignition (HEI) system is a pulse-triggered, transistor controlled, inductive discharge ignition system. The entire HE! system is contained within the distribu. tor cap. The distributor, in addition to housing the mechanical and vacuum advance mechanisms, contains the ignition coil, the

electronic control module, and the magnetic triggering device. The magnetic pick-up assembly contains a permanent magnet, -a pole piece with internal teeth, and a pick-up coil (not be be confused with the ignition coil). In the HEI system, as in other electronic ignition systems, the breaker points have been replaced with an electronic switch — a transistor — which is located within the control module. This switching transistor performs the same function ~ as the points in a conventional ignition system; it simply turns coil primary current on and off at the correct time. Essentially, electronic and conventional ignition systems operate on the same basic principle. The module which houses the switching transistor is controlled (turned on and off) by a magnetically generated impulse induced in the pick-up coil. When the teeth of the rotating timer align with the teeth of the pole piece, the induced voltage in the pick-up coil signals the electronic module to open the coil primary circuit. The primary current then decreases,

and a high voltage is induced in the ignition coil secondary windings which is then directed through the rotor and spark plug wires to fire the spark plugs. The pick-up coil module system simply replaces the conventional breaker points and condenser. The condenser found within the distributor is for radio suppression purposes only and has nothing to do with the ignition process. The module automatically controls the dwell period, increasing it with increasing engine speed. Since dwell is automatically controlled, it cannot be adjusted. The module itself is non-adjustable and non-repairable and must be replaced if found defective.

HE! SYSTEM PRECAUTIONS Before going on to troubleshooting, it might be a good idea to. take note of the following: e Timing Light Use — Inductive pick-up timing lights are

the best kind to use with HEI. Timing lights which connect between the spark plug wire occasionally (not always) give

false readings. e Spark Plug Wires — The plug wires used with HEI systems are of a different construction than conventional wires. When replacing thém, make sure you get the correct wires, since conventional wires won't carry the voltage. Also handle them carefully to avoid cracking or splitting them and never pierce them. i

9-12

ENGINE PERFORMANCE AND TUNE-UP

85772025

Fig. 13 Exploded view of a typical HEI distributor assembly equipped with integral coil

e Tachometer Use — Not all tachometers will operate or indicate correctly when used on a HEI system. While some tachometers may give a reading, this does not necessarily mean the reading is correct. In addition, some tachometers hook up differently from others. If you can’t figure out whether or not your tachometer will work on your truck, check with the tachometer manufacturer. Dwell readings have no significance at all. . e HEI System Testers — Instruments designed specifically for testing HEI systems are available from several tool manufacturers. Some of these will even test the module itself. However, the test given in the following section will require only an ohmmeter and a voltmeter.

Troubleshooting the HEI System The symptoms of a defective component within the HEI system are exactly the same as those you would encounter in a conventional system. Some of these symptoms are:

e Hard or no Starting e Rough Idle e Fuel Poor Economy

e Engine misses under load or while accelerating

If you suspect a problem in the ignition system, there are certain preliminary checks which you should carry out before you begin to check the electronic portions of the system. First, it is extremely important to make sure the vehicle battery is in a good state of charge. A defective or poorly charged battery will cause the various components of the ignition system to read incorrectly when they are being tested. Second, make sure all wiring connections are clean and tight, not only at the battery, but also at the distributor cap, ignition coil, and at the electronic control module. Since the only change between electronic and conventional ignition systems is in the distributor component area, it is imperative to check the secondary ignition circuit first. If the secondary circuit checks out properly, then the engine condition is probably not the fault of the ignition system. To check the secondary ignition system, perform a simple spark test. Remove one of the plug wires and insert some sort of extension in the plug socket. An old spark plug with the ground electrode removed makes a good extension. Using a pair of insulated pliers, hold the wire and extension about ‘/4 inch away from the block and crank the engine. If a normal spark occurs, then the problem is most likely not in the ignition system. Check for fuel system problems, or fouled spark plugs. If, however, there is no spark or a weak spark, then further ignition system testing will have to be done. Troubleshooting techniques fall into two categories, depending on the nature of the problem. The categories are (1) Engine cranks, but won't start or (2) Engine runs, but runs rough or cuts out.

ENGINE FAILS TO START If the engine won't start, perform a spark test as described earlier. If no spark occurs, check for the presence of normal battery voltage at the battery (BAT) terminal in the distributor cap. The ignition switch must be in the ON position for this test. Either a voltmeter or a test light may be used for this test. Connect the test light wire to ground and the probe end to the BAT terminal at the distributor. If the light comes on, you have voltage to the distributor. If the light fails to come on, this indicates an open circuit in the ignition primary wiring leading to the distributor. In this case, you will have to check

wiring continuity back to the ignition switch using a test light. If there is battery voltage at the BAT terminal, but no spark at the plugs, then the problem lies within the distributor assembly. Go on to the distributor components test section.

ENGINE RUNS ROUGH OR CUTS OUT 1. Make sure the plug wires are in good shape first. There should be no obvious cracks or breaks. You can check the

plug wires with an ohmmeter, but do not pierce the wires with + a probe. Check the chart for the correct plug wire resistance.

ENGINE PERFORMANCE AND TUNE-UP

2-13

HE! Plug Wire Resistance

; Wire Length eR 0-15 inches 15-25 inches

25-35 inches

Chart

OHMMETER

OHMMETER

PICKUP COIL

Minimum ee ee a 3000 ohms 4000 ohms

6000 ohms

Over 35 inches

LEADS DISCONNECTED

Maximum ee 10,000 ohms 15,000 ohms

9

20,000 ohms

O

aS

dy

25,000 ohms

}

Mee 5:

4-TERMINAL 2

CONNECTOR

8577204C

2. If the plug wires are OK, remove the cap assembly, and check for moisture, cracks, chips, or carbon tracks, or any other high voltage leaks or failures. Replace the cap if you find any defects. Make sure the timer wheel rotates when the engine is cranked. If everything is all right so far, go on to the distributor components test section.

. ; Distributor Components Testing » See Figures 14 and 15

MODULE PICKUP COIL

ASSEMBLY

lf the trouble has been narrowed down to the components within the distributor, the following tests can help pinpoint the defective component. An ohmmeter with both high and low ranges should be used. These tests are made with the cap assembly removed and the battery wire disconnected. 1. Connect an ohmmeter between the TACH and BAT terminals in the distributor cap. The primary coil resistance should be less than 1.0 ohm (zero or nearly zero). 2. To check the coil secondary resistance, connect an ohmmeter between the rotor button and the BAT terminal. Then - connect the ohmmeter between the ground terminal and the rotor button. The resistance in both cases should be between 6,000 and 30,000 ohms. 3. Replace the coil only if the readings in step one and two are infinite.

85772031

These resistance checks will not disclose shorted coil windings. This condition can be detected only with scope analysis or a suitably designed coil tester. If these instruments are unavailable, replace the coil with a known good coil as a final coil test. 4. To test the pick-up coil, first disconnect the white and green module leads. Set the ohmmeter on the high scale and connect it between a ground and either the white or green lead. Any resistance measurement less than infinity requires replacement of the pick-up coil. 5. Pick-up coil continuity is tested by connecting the ohmmeter (on low range) between the white and green leads. Normal resistance is between 500 and 1500 ohms. Move the vacuum advance arm while performing this test. This will de- tect any break in coil continuity. Such a condition can cause intermittent misfiring. Replace the pick-up coil if the reading is outside the specified limits. 6. If no defects have been found at this time, and you still have a problem, then the module will have to be checked. If you do not have access to,a module tester, the only possible

OHMMETER 85772030

Fig. 14 Checking coil resistance on the HEI system. Ohmmeter 1 shows the primary coil resistance connection. Ohmmeter 2 shows the secondary resistance connection. 1980 models shown, otherssimilar

a Se

9-14.

ENGINE PERFORMANCE AND TUNE-UP

a

alternative is a substitution test. If the module fails the substitution test, replace it.

Component Replacement INTEGRAL IGNITION COIL » See Figures 16, 17, 18, 19, 20, 21 and 22 The integral ignition coil may be removed with the distributor cap installed in the vehicle or with the cap removed for easy access. If the coil is removed with the cap still installed on the distributor, some of the below steps may be skipped as noted. 1. Disconnect the negative battery cable. 2. Remove the ignition wire set retainer from the top of the distributor cap. If the cap is being removed from the vehicle, keep the spark plug wires attached to the retainer for ease of installation.

———_—

4. If the cap is being removed, release the four latches by depressing and turning using a screwdriver, then remove cap and coil assembly from the distributor housing. 5. Remove ignition coil cover attaching screws and lift the cover off the distributor cap. 6. Remove ignition coil attaching screws. Using a pair of needle nose pliers, carefully lift the coil with leads from the end of the cap. 7. Remove the ignition coil assembly from the cap, then remove the arc seal. 8. Clean with soft cloth and inspect cap for defects. Replace cap, if needed.

elf distributor is not equipped with a spark plug wire set retainer, it will be less hassle to remove the coil while the

cap is still installed in the vehicle. If the cap must be removed, the spark plug wires should be tagged to assure proper installation. 85772060

3. If the cap is being removed from the vehicle, disconnect the feed and module terminal wire connectors from the distributor cap.

Fig. 18 Once the screws are removed, lift the cover from the distributor cap for access to the ignition coil

Fig. 19 Loosen and remove the screws attaching the ignition coil to the distributor cap

85772062

Fig. 17 There should be at least 2 screws on most coil covers. The rear screw may be more difficult to access

Fig. 20 Make sure all 4 screws are removed before trying the separate the coil from the cap

ENGINE PERFORMANCE AND TUNE-UP 215 SS

Sa

SSS

SSS

SSS

¢ 85772063

Fig. 21 Needle nose pliers may be used to withdraw the coil leads from the cap

Fig. 24 Using a screwdriver, carefully release the locktab on the outer distributor electrical connector

85772064

Fig. 22 Be careful to just remove the coil leads and not to excessively stretch or bend the wires 9. To install the new coil and cover into the cap, reverse the Steps for removal.

DISTRIBUTOR CAP » See Figures 23, 24, 25, 26, 27, 28 and 29 1. Disconnect the negative battery cable. 2. Remove the retainer and spark plug wires from the cap. Be sure to note the cap position and spark plug wire location. If the vehicle is not equipped with a wire retainer, the spark plug wires should be labelled to assure proper installation. 3. Use a screwdriver to carefully release the locktabs and disconnect the wiring harness connectors from the distributor cap. 4. Depress and release the 4 distributor cap-to-housing retainers and lift off the cap assembly. 5. Remove the 4 coil cover screws and cover. 6. Using a finger or a blunt tip, push the spade terminals up out of the distributor cap. 7. Remove all 4 coil screws and lift the coil, coil spring and rubber seal washer out of the cap coil cavity. 8. Using a new distributor cap, reverse the above proce-

Fig. 25 Once the locktab is released, grasp and withdraw the connector by hand

ROTOR

o-

» See Figures 30 and 31 1. Disconnect the negative battery cable. 2. Disconnect the wiring harness connectors and module wire connectors from the distributor. =>On some vehicles the spark plug wires may contain too; little play to reposition the cap with them attached. If so, it may be necessary to remove the distributor cap completely for access to the rotor. As always, if there is no retainer, be sure to tag all wires before disconnecting them from the cap.

dures to assemble, being sure to clean and lubricate the rub-

ber seal with dielectric lubricant.

85772065

Fig. 23 If the wire retainer is missing, be sure to tag the spark plug wires before they are disconnected from the cap

9-16 ENGINE PERFORMANCE AND TUNE-UP

5772071

Fig. 29 With all wiring disconnected and the latches released, the distributor cap may be lifted from the distributor assembly

Fig. 26 The inner connector is released in the same

manner as the outer connector, but be careful the

locktabs are easy to break off

070

Fig. 27 With the locktab released, the inner connector may be removed by hand

Fig. 30 Using a screwdriver, loosen and remove the rotor retaining screws

85772073

ier

Fig. 31 The rotor should be checked for wear or corro-

Fig. 28 Use a screwdriver to release the distributor cap latches by depressing and turning counterclockwise

sion. If the rotor is in question, it is best to replace it.

3. Depress and release the 4 distributor cap to housing retainers and lift off the cap assembly with the spark plug wires attached. Reposition the cap and wires for access to the rotor. 4. Remove the two rotor attaching screws and rotor.

=> magnetic tipped screwdriver will greatly reduce the risk of dropping and loosing the screws behind the dis-

tributor housing and engine. 5. Reverse the above procedure to install.

VACUUM ADVANCE » See Figures 32, 33 and 34 1. Disconnect the negative battery cable. 2. Remove the distributor cap and rotor as previously

described. 3. Disconnect the vacuum hose from the vacuum advance

unit. 4. Remove the two vacuum advance retaining screws, pull the advance unit outward, rotate and disengage the operating rod from its tang. 5. Reverse the above procedure to install.

ENGINE PERFORMANCE AND TUNE-UP 217 SS

2074

Fig. 32 Disconnect the hose from the vacuum advance unit

85772077

Fig. 35 Remove the ignition module retaining screws

85772075

_Fig. 33 Remove the advance unit retaining screws. The ignition module was removed for clarity only.

85772078

Fig. 36 Remove the capacitor retaining screw

To install:

Bt.

5. Install module, wiring harness, and capacitor assembly. Use silicone dielectric lubricant on housing under module.

Failure to use the silicone dielectric lubricant on the ignition module will drastically shorten the ignition module’s life.

85772076

Fig. 34 Separate the advance unit linkage from the distributor and remove it from the vehicle

6. Install the rotor to the distributor assembly. 7. Install the distributor cap and wires. 8. Connect the negative battery cable.

IGNITION MODULE » See Figures 35, 36, 37, 38, 39 and 40

1. Disconnect the negative battery cable. 2. Remove the distributor cap and rotor as previously outlined in this Section. 3. Remove two module attaching screws and the capacitor attaching screw. Lift module, capacitor and harness assembly

:

from base.

4. Disconnect wiring harness from module. If access is difficult, the module assembly may by pivoted upwards as the

harness allows.

“85772079

Fig. 37 Lift the capacitor and module assembly from the distributor housing

2-18 ENGINE PERFORMANCE AND TUNE-UP EE

ee » See Figure 41 Timing should be checked at each tune-up and any time the HEI system is serviced although it isn’t likely to change much. The timing marks consist of a notch on the rim of the crank-

shaft pulley or vibration damper and a graduated scale attached to the engine front (timing) cover. A inductive pickup timing light must be used, as a neon(static light) is too inaccurate. The inductive pickup clamps around the No. 1 spark plug wire, sensing the surges of high voltage electricity as they are sent to the plug. The advantage of this type of light is that no mechanical connection is inserted between the wire and the plug, which eliminates false signals to the timing light. Some timing lights have other features built into them, such as dwell meters or tachometers. These are convenient, in that

they reduce the tangle of wires under the hood when you’re working, but may duplicate the functions of tools you already have.

Inspection and Adjustment

85772080

Fig. 38 Disengage the module harness connector

To check and adjust the timing: 1. Warm up the engine to normal operating temperature. Stop the engine and connect the timing light to the No. 1 (left front on V8, front on six) spark plug wire. Numbering is illustrated in this Section. Under no circumstances should the spark plug wire be pierced to hook up a timing light. Clean off the timing marks and mark the pulley or damper notch and timing scale with white chalk. The timing notch on the pulley or damper can be elusive. The best way to get it to an accessible position for marking is to bump the engine around using either the ignition key or a remote starter. 2. Disconnect and plug the vacuum line at the distributor. This is done to prevent any distributor vacuum advance. A short screw, pencil, or a golf tee can be used to plug the line. 3. Start the engine and adjust the idle speed to that specified in the Tune-Up Specifications chart. With automatic transmission, set the specified idle speed in Park. It will be too high, since it is normally (in most cases) adjusted in Drive. However, it is safer to adjust the timing in Park and to reset

85772:

Fig. 39 If the module is to be replaced, separate the module from the capacitor assembly

the idle speed after all timing work is done. Some trucks require that the timing be set with the transmission in Neutral. Refer to the Tune-Up Specifications chart or the underhood sticker for details. You can disconnect the idle solenoid, if

equipped, to get the speed down. Otherwise, adjust the idle

CAPACITOR ATTACHING

85772034

Fig. 40 Be sure to coat the mating surfaces with silicone lubricant when replacing the HEI] module

85772035

Fig. 41 Timing marks (on pulley) and timing indicator on 1980 and later gasoline V8’s

ENGINE PERFORMANCE AND TUNE-UP

2-19

speed screw. This is done to prevent any centrifugal (mecharical) advance.

timing mark (see the Tune-Up Specifications chart), the timing will have to be adjusted.

Never ground the HEI TACH terminal; serious system damage will result.

->*TDC or or BTDC, BEFORE. shown as

4. Aim the timing light at the pointer marks. Be careful not to touch the fan, because it may appear to be standing still Keep the timing light wires clear of the fan, belts, and pulleys. If the pulley or damper notch isn't aligned with the proper

Top Dead Center corresponds to 0 degrees. B, or Before Top Dead Center may be shown as A, or ATDC, or After Top Dead Center may be AFTER.

5. Loosen the distributor base clamp locknut. You can buy a special wrench which makes this task a lot easier on V8s. Turn the distributor slowly to adjust the timing, holding it by the body and not the cap. Turn the distributor in the direction of rotor rotation (found in the Firing Order illustration in this Section) to retard, and against the direction of rotation to advance. 6. Tighten the locknut. Check the timing again, in case the distributor moved slightly as you tighten it. 7. Replace the distributor vacuum line. Correct the idle speed. 8. Stop the engine and disconnect the timing light.

DIESEL INJECTION TIMING Injection Pump Timing » See Figures 42 and 43 For the diesel engine's fuel injection system to be properly timed, the marks on the top of the engine front cover (8-379) or injection pump adapter (8-350) must be aligned with the marks on the injection pump flange. The engine must be off when the timing is reset. >On 49 state 8-379s, the marks on the top of the engine

20 Fila BS

25 FT. LBS. (34 NM)

front cover are scribe lines. On California 8-379s, the marks are half-circles.

1. Loosen the three pump retaining nuts. If the marks are not aligned, adjustment is necessary. 2. Loosen the three pump retaining nuts. Special Tool #J-26987 is useful here on the 8-350. 3. Align the mark on the injection pump with the mark on the front cover (8-379) or adapter (8-350). Tighten the nuts to 30 ft. Ibs. on the 8-379, and 35 ft. Ibs. on the 8-350.

Zs,

TIMING

18FT.LBS.

MARK — (24NM)

CLIP

25 FT. LBS. INJECTION. (34 NM) PUMP (USE BACK-UP ADAPTER VIEWA ALIGN MARKS

WRENCH ON UPPER INJECTION

(MAXIMUM ALLOWABLE NOZZLE HEX) OFFSET IN EITHER DIRECTION SHOWN) 85772037

Fig. 43 Injection pump timing marks location and alignment, 350 diesel shown

85772036

Fig. 42 Diesel injection timing marks, 379 shown. Marks shown are in alignment

e>Use a 3x” inch open-end wrench on the nut at the front of the injection pump to aid in rotating the pump to align the marks. 4. Adjust the throttle linkage if necessary.

9-20

ENGINE PERFORMANCE AND TUNE-UP

ae

and need to be replaced. In the event of cylinder head removal or any operation that requires disturbing or removing the rocker arms, the rocker arms must be adjusted so the lifters may perform their job of maintaining zero lash. Please refer to Section 3 for these procedures.

All engines covered in this manual are equipped with hydraulic valve lifters. Engines so equipped operate with zero clearance in the valve train which is maintained by the lifters themselves. Therefore, the hydraulic lifters do not require any adjustment as part of the normal tune-up, although they occasionally become noisy (especially on high mileage engines)

IDLE SPEED AND MIXTURE ADJUSTMENTS | Carbureted Engines In most cases, the mixture screws have limiter caps, but in

later years the mixture screws are concealed under staked in plugs. Idle mixture is adjustable only during carburetor overhaul, and requires the addition of propane as an artificial mixture. For these reasons, mixture adjustments are not covered here for affected models. See the emission control label in the engine compartment for procedures and specifications not supplied here. See Carburetor Identification in Section 6 for carburetor |.D. specifics.

1980-87

1)

ENGINE MUST BE WARM-CHOKE WIDE OPENCAM FOLLOWER OFF STEPS OF CAM (SEE EMISSION LABEL)

Ne

TO ADJUST BASE 1OLE, TURN 1/6” HEX SCREW (SOLENOID NOT ENERGIZED)

SET CURB IDLE TO SPECIFICATIONS TURN ASSEMBLY IN OR OUT TO ADJUST RPM. (SOLENOID ENERGIZED)

85772042

Fig. 44 Idle speed adjustment for 250 and 292 six cylinder, 1980 and later

» See Figures 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55 and 56 © TO ADJUST LOW

Idle mixture is not adjustable in these years, except for the heavy duty emission 292 6-cylinder equipped with the IME carburetor, and heavy duty emission V8s equipped with the four barrel M4MC.

IDLE TURN 178"

HEX SCREW

(SOLENOID NOT ENERGIZED) ® NOTE: ENGINE MUST BE WARM — CHOKE WIDE OPEN — FAST IDOLE CAM FOLLOWER OFF STEPS OF CAM (SEE EMISSION LABEL)

HEX WRENCH

6-250 Engine

1. All adjustments should be made with the engine at normal operating temperature, air cleaner on, choke open, and air

® SET CURB IDLE TO SPECIFICATIONS —TURN ASSEMBLY IN OR OUT TO ADJUST R.P.M (SOLENOID ENERGIZED)

conditioning off, unless otherwise noted.

2. Set the parking brake and block the rear wheels. 3. Automatic transmissions should be set in Drive, manuals in Neutral, unless otherwise noted in the procedures or in the Tune-Up Specifications chart, or on the emission control label. 4. Check the emission control label for any special instructions. 5. Open the throttle slightly to allow the solenoid plunger to extend. 6. Turn the solenoid screw to adjust the curb idle to the figure given in the Tune-Up Specifications chart or on the emission control label. 7. Disconnect the electrical connector from the solenoid. The idle speed will drop. 8. Adjust the idle to the basic idle speed figure given on the emission control label by means of the idle speed screw. 9. Shut off the engine and reconnect the solenoid.

85772044

Fig. 45 1980 and later in-line six cylinder idle speed adjustment, MV and ME-type 2-bbls, 6-292 Engine

IDLE SPEED 1. All adjustments should be made with the engine at normal operating temperature, air cleaner on, choke open, and air conditioning off, unless otherwise noted. 2. Set the parking brake and block the rear wheels. 3. Automatics should be place in Drive, manuals in Neutral, except as noted in the Tune-Up Specifications chart. 4. Make certain that the fast idle follower is not on any of the steps marked H, 2, or L on the cam. It should be resting against the first step below L. 5. Set the idle to specifications by turning the solenoid in or out. Do this with a wrench on the nut attached to the end of the solenoid body. 6. Disconnect the electrical connector from the solenoid. The engine speed will drop.

ENGINE PERFORMANCE AND TUNE-UP

2-21

FAST IDLE ADJUSTMENT

4) SUPPORT LEVER WITH PLIERS — BEND TANG IN OR OUT TO OBTAIN SPECIFIED FAST IDLE R.P.M. (SEE INSERT).

®@ PLACE CAM FOLLOWER TANG ON HIGH STEP OF CAM (SEE NOTE).

MANUAL CHOKE MODELS WITH SMOOTH CONTOUR CAM SURFACE — ROTATE FAST IDLE CAM CLOCKWISE TO ITS FARTHEST UP POSITION.

D prepare VEHICLE FOR ADJUSTMENTS — SEE EMISSION LABEL ON VEHICLE. IGNITION TIMING SET PER LABEL. HIGH

FASTIDLECAM

STEPS

® aosust CURB IDLE SPEED WITH IDLE STOP SOLENOID.

ie {|

85772053

Fig. 46 1 ME 1-bbl fast idle adjustment 7. inside speed 8.

With a ‘s inch Allen head wrench, turn the screw located the nut attached to the solenoid body, and set the idle to the specification on the emission label Reconnect the solenoid wire.

IDLE MIXTURE 1. Set the parking brake and block the rear wheels. 2. Remove the air cleaner but do not disconnect any of the hoses. Disconnect and plug the other hoses as directed on the emission control label. 3. The engine should be at normal operating temperature, choke open, and air conditioning off, if equipped. Connect an accurate tachometer to the engine. 4. Disconnect and plug the vacuum advance hose at the distributor and check the ignition timing. Correct as necessary. Reconnect the vacuum advance hose. 5. Carefully remove the limiter cap from the idle mixture screw. Lightly seat the screw, then back it out just enough to allow the engine to run. 6. Place the transmission in Neutral. 7. Back the mixture screw out ‘ turn at a time until the maximum idle speed is obtained. Adjust the idle speed to the figure given on the emission control label by means of the idle speed screw. Repeat this step until you are certain that the maximum speed has been obtained with the mixture screw. 8. Turn the mixture screw in ‘s turn at a time until the idle speed drops to the figure given on the emission control label. 9. Reset the idle speed to the figure given on the emission control label by means of the idle speed screw. Check and adjust the fast idle as directed on the emission control label. Reconnect any vacuum hoses removed in Step 2, install the

air cleaner, and recheck the idle speed. Correct, if necessary, by means of the idle speed screw. 8-305 Engine

1. All adjustments should be made with the engine at normal operating temperature, air cleaner on, choke open, and air conditioning off, unless otherwise noted. 2. Set the parking brake and block the rear wheels. 3. Automatic transmissions should be set in Drive, manuals

in Neutral, unless otherwise noted in the procedures or in the Tune-Up Specifications chart, or on the emission control label. 4. Check the emission control label for any special instructions or to determine which hoses, if any, must be

disconnected. 5. Make sure the idle speed screw is on the low (L) step of the fast idle cam. 6. For vehicles without air conditioning, do the following: a. Turn the idle speed screw to adjust idle speed to the specification found in the Tune-Up Specifications chart or on the underhood emissions sticker. b. Open the throttle slightly to allow the solenoid plunger to extend. c. Turn the solenoid screw to adjust the curb idle to specification, as given in the chart or on the emission control sticker in the engine compartment. d. Then disconnect the electrical connector from the solenoid. The idle speed will drop. e. Turn the idle speed screw to set the slow engine idle to the figure given on the emission control sticker. f. Reconnect the solenoid and shut off the engine.

ENGINE PERFORMANCE AND TUNE-UP

9-22

@ RECONNECT ELECTRICAL

@ DISCONNECT ELECTRICAL LEAD FROM IDLE SPEED SOLENOID (IF SO EQUIPPED).

LEAO TO IDLE SPEED SOLENOID.

7. For vehicles equipped with air conditioning, do the following: a. Turn the idle speed screw to set the idle to specifications. b. Disconnect the air conditioner compressor electrical lead at the compressor, and turn the air conditioner on. c. Open the throttle slightly to allow the solenoid plunger to fully extend. d. Turn the solenoid screw and adjust to the specification on the engine emission label. e. Reconnect the air conditioner compressor lead. 8. Reconnect any hoses that were disconnected. 8-350, 8-400, and 8-454 Engines

IDLE SPEED ADJUSTMENT ADJUST BASE IDLE SPEED SCREW TO R.P.M. SPECIFIED ON EMISSION LABEL (AUTOMATIC TRANSMISSION IN DRIVE OR MANUAL TRANSMISSION IN NEUTRAL). 85772047

Fig. 47 1980-81 V8 2-bbl (M2MC) idle speed adjustment with solenoid

SOLENOID PLUNGER TOFULLvexTtNo _——- © TUANIDLE SPEEDSCREWTO

® OPEN THROTTLE

(©)SOLENOID

SLIGHTLY TO ALLOW

ae

ENERGIZED -

A/C COMPRESSOR

THROTTLE

DISCONNECTED AT A/C COMPRESSOR, A/C ON, A/T TRANSMISSION

DRIVE, M/TIN

SPECIFICATIONS

— A/C OFF

(SEE EMISSION LABEL)

LEAD

© f

IN

NEUTRAL

Ne \ ‘\3 D

ud

ELECTRICAL CONNECTION

® TURN SOLENOID SCREW TO ADJUST TO SPECIFIED RPM (RECONNECT A/C COMPRESSOR LEAD AFTER ADJUSTMENT)

@

PREPARE VEHICLE FOR ADJUSTMENTS — SEE EMISSION LABEL ON VEHICLE. NOTE IGNITION TIMING SET PER LABEL. 85772048

1. All adjustments should be made with the engine at normal operating temperature, air cleaner on, choke open, and air conditioning off, unless otherwise noted.

2. Set the parking brake and block the rear wheels. 3. Automatics should be place in Drive, manuals in Neutral, except as noted in the Tune-Up Specifications chart. 4. Check the underhood emissions sticker to determine which hoses, if any, must be disconnected. 5. For two barrel carburetors, make sure that the idle speed screw is on the low(L) step of the fast idle cam. 6. For vehicles without air conditioning, do the following: a. Turn the idle speed screw to adjust idle speed to the specification found in the Tune-Up Specifications chart or on the underhood emissions sticker. b. Open the throttle slightly to allow the solenoid plunger to extend. c. Turn the solenoid screw to adjust the curb idle to specification, as given in the chart or on the emission control sticker in the engine compartment. d. Then disconnect the electrical connector from the sole-, noid. The idle speed will drop. e. Turn the idle speed screw to set the slow engine idle to the figure given on the emission control sticker. f. Reconnect the solenoid and shut off the engine. 7. For vehicles equipped with air conditioning, do the following: a. Turn the idle speed screw to set the idle to specifications. b. Disconnect the air conditioner compressor electrical lead at the compressor, and turn the air conditioner on. c. Open the throttle slightly to allow the solenoid plunger to fully extend. d. Turn the solenoid screw and adjust to the specification on the emission control label and the Tune-Up Specifications chart. e. Reconnect the air conditioner compressor lead. 8. Reconnect any hoses that were disconnected.

IDLE MIXTURE ADJUSTMENT

Fig. 48 2GC 2-bbl slow idle adjustment, A/C equipped

Mixture is adjustable on heavy duty emissions V8s with the four barrel M4MC carburetor. This procedure will not work on light duty emissions trucks. 1. The engine must be at normal operating temperature, choke open, parking brake applied, and the transmission in Park or Neutral. Block the rear wheels and do not stand in front of the truck when making adjustments.

ENGINE PERFORMANCE AND TUNE-UP

© prepare VEHICLE FOR ADJUST. MENTS - SEE EMISSION LABEL ON VEHICLE. NOTE: IGNITION TIMING SET PER LABEL.

© PREPARE VEHICLE FOR ADJUSTMENTS SEE EMISSION LABEL ON VEHICLE. oONOTE: ; IGNITION TIMING SET PER LABEL SOLENOID ENERGIZED - A/T IN DRIVE AITININEUTORE ce

TURN TO SETIOLE BASICSPEED IDLE SCREW SPEED TO SPECIFICATIONS (SOLENOID DE-ENERGIZED)

‘

a

©

CO}

«

ae,

® TURN FAST IDOLE SCREW iN OR OUT TO OBTAIN

SPECIFIED FAST IDLE

_, er,

~>>=

Q

‘

© RECONNECT SOLENOID ELECTRICAL LEAD AFTER ADJUSTMENT

ts 2 we

@ turn SOLENOID SCREW TO ADJUST CURB IDLE SPEED TO SPECIFIED RPM (SOLENOID ENERGIZED) PUACE FAST IDLE

SCREW ON HIGHEST STEP OF FAST IDLE CAM

Be

3

OPEN THROTTLE SLIGHTLY TO ALLOW SOLENOID PLUNGER TO FULLY EXTEND

IDLE SPEED ADJUSTMENT

WITH A/C (ON VEHICLE) IDOLE SPEED ADJUSTMENT WITHOUT A/C (ON VEHICLE)

FAST IDLE ADJUSTMENT (ON VEHICLE)

@) prepare VEHICLE FOR ADJUSTMENTS SEE EMISSION LABEL ON VEHICLE.

NOTE: IGNITION TIMING SET PER LABEL. (2) TURN IDLE SPEED SCREW

TO SET CURB IDLE SPEED TO SPECIFICATIONS (SEE EMISSION LABEL)

85772049

Fig. 49 2SE 2-bbl idle speed and fast idle adjustments

(3) SOLENOID ENERGIZED - A/C (4) PREPARE VEHICLE FOR ADJUSTMENTS SEE EMISSION LABEL ON VEHICLE. NOTE: IGNITION TIMING SET PER LABEL.

COMPRESSOR LEAD DISCONNECTED AJ A/C COMPRESSOR, A/C ON, ‘ A/T IN DRIVE, M/T IN NEUTRAL.

(5) TURN SOLENOID SCREW TO ADJUST TO SPECIFIED RPM. (RECONNECT A/C COMPRESSOR LEAD

\} AFTER ADJUSTMENT). (V\, _ fe

@) TURN IDLE SPEED SCREW TO SET CURB IDLE SPEED TO SPECIFICATIONS ~- A/C OFF (SEE EMISSION LABEL)

OPEN THROTTLE SLIGHTLY TO ALLOW SOLENOID PLUNGER TO FULLY EXTEND.

ELECTRICAL CONNECTION

85772050

Fig. 50 E2SE 2-bbl idle speed adjustment with A/C, 1983

2-23

9-24

ENGINE PERFORMANCE AND TUNE-UP

®@ PREPARE VEHICLE FOR ADJUSTMENTS SEE EMISSION LABEL ON VEHICLE. NOTE: IGNITION TIMING SET PER LABEL

@ TURN SOLENOID SCREW TO ADJUST CURB IDLE SPEED TO SPECIFIED RPM (SOLENOID ENERGIZED) SOLENOID ENERGIZED - A/T IN DRIVE, M/T IN

DISCONNECT SCONNEC

© TURN IDLE SPEED SCREW

TO SET BASIC IDLE SPEED TO SPECIFICATIONS. RECONNECT SOLENOID ELECTRICAL LEAD AFTER ADJUSTMENT

OPEN THROTTLE SLIGHTLY TO ALLOW SOLENOID PLUNGER TO FULLY EXTEND

sie ee ee eorensic

85772051

Fig. 51 E2SE 2-bbl idle speed adjustment without A/C

(1) PREPARE VEHICLE FOR ADJUSTMENTS SEE EMISSION LABLE ON VEHICLE. PLACE TRANSMISSION IN PARK/NEUTRAL. (Sirvy

fF

~

“

C

PLACE FAST IDLE SCREW ON HIGHEST STEP OF FAST IDLE CAM.

(3) TURN FASTIDLESCREW IN OR OUT TO OBTAIN SPECIFIED FAST IDLE R.P.M. - (SEE LABEL).

©

85772052

Fig. 52 E2SE fast idle adjustment

ENGINE PERFORMANCE AND TUNE-UP ® BOLENDID ENERGIZED — CcCOMPRESSOR LEAD DISCONNECTED ATA/C COMPRESSOR, A/C ON. A/T TRANSMISSION IN DRIVE, M/T IN NEUTRAL

2-25

@ PREPARE VEHICLE FOR ADJUSTMENTS — SEE EMISSION LABEL ON VEHICLE. NOTE: IGNITION TIMING SET PER LABEL.

(S) TURN SOLENOID SCREW TO ADJUST TO SPECIFIED RPM. (RECONNECT A/C COM neseon LEAD AFTER ADJUSTMEN

772082

Fig. 53 Adjusting the slow idle speed on a 1984 4bbl carburetor. The adjustment should be made with air cleaner installed, but was removed in this picture for clarity

SOLENOID PLUNGER TO FULLY EXTEND (SEE EMISSION LABEL)

85772046

Fig. 56 1980 and later 4-bbl adjustments with solenoid

Throttle Body Injection (TBI) Engines The throttle body injected vehicles are controlled by a computer which supplies the correct amount of fuel during all engine operating conditions; no adjustment is necessary.

Diesel Engine 85772083

Fig. 54 Adjusting the fast idle speed on a 1984 4bbl carburetor. The adjustment should be made with air cleaner installed, but was removed in this picture for

clarity

IDLE SPEED ADJUSTMENT 350 Engine

» See Figure 57

TURN IOLE SPEED SCREW TO SET CURB IDLE SPEED TO SPECIFICATIONS — A/C OFF (SEE EMISSION LABEL)

©

:

prepare VEHICLE FOR AOJUSTMENTS — SEE EMISSION LABEL ON VEHICLE. NOTE: IGNITION TIMING SET PER LABEL.

85772045

Fig. 55 1980 and later 4-bbl adjustments without solenoid; 1980-81 V8 2-bbl (M2MC) models 2. Remove the air cleaner. Connect a tachometer and a vacuum gauge to the engine. 3. Turn the idle mixture screws in lightly until they seat, then back them out two turns. Be careful not to tighten the mixture screw against its seat, or damage may result. 4. Adjust the idle speed screw to obtain the engine rpm figure specified on the emission control label. 5. Adjust the idle mixture screws equally to obtain the highest engine speed. 6. Repeat Steps 4 and 5 until the best idle is obtained. 7. Shut off the engine, remove the tachometer and vacuum gauge, and install the air cleaner.

A special tachometer with an RPM counter suitable for the 8-350 V8 diesel is necessary for this adjustment; a standard tach suitable for gasoline engines will not work. 1. Place the transmission in Park, block the rear wheels and firmly set the parking brake. 2. If necessary, adjust the throttle linkage as described in Section 6. 3. Start the engine and allow it to warm up for 10-15 minutes. 4. Shut off the engine and remove the air cleaner. 5. Clean off any grime from the timing probe holder on the front cover; also clean off the crankshaft balancer rim. 6. Install the magnetic probe end of the tachometer fully into the timing probe holder. Complete the remaining tachometer connections according to the tach manufacturer’s instructions. 7. Disconnect the two-lead connector from the generator. 8. Make sure all electrical accessories are OFF.

e>At no time should either the steering wheel or the brake pedal be touched. 9. Start the engine and place the transmission in Drive (after first making sure the parking brake is firmly applied). 10. Check the slow idle speed reading against the one printed on the underhood emissions sticker. Reset if necessary. 11. Unplug the connector from the fast idle cold advance (engine temperature) switch, and install a jumper wire between the connector terminals. DO

NOT allow the jumper to ground.

) TUNE-UP 2-26 ENGINE PERFORMANCE AND EN nliaseemi einemanna eiaalaheteeretmn a 12. Check the fast idle speed and reset if necessary according to the specification printed on the underhood emissions sticker. 13. Remove the jumper wire and reconnect it to the temperature switch. 14, Recheck the slow idle speed and reset if necessary. 15. Shut off the engine. 16. Reconnect the leads at the generator and A/C compressor. ; 17. Disconnect and remove the tachometer. 18. If the car is equipped with cruise control, adjust the servo throttle rod to minimum slack, then put the clip in the first free hole closest to the bell rank or throttle lever. 19. Install the air cleaner.

379 V8 Engine

» See Figure 58 mA special tachometer suitable for diesel engines must be used. A gasoline engine type tach will not work with the diesel engine.

2. Run the engine up to normal operating temperature. The air cleaner must be mounted and all accessories turned off. 3. Install the diesel tachometer as per the manufacturer's instructions. 4. Adjust the low idle speed screw on the fuel injection pump to 650 rpm in Neutral or Park for both manual and automatic transmissions.

e» All idle speeds are to be set within 25 rpm of the specified values. 5. Adjust the fast idle speed as follows: a. Remove the connector from the fast idle solenoid. Use an insulated jumper wire from the battery positive terminal to the solenoid terminal to energize the solenoid. b. Open the throttle momentarily to ensure that the fast idle solenoid plunger is energized and fully extended. c. Adjust the extended plunger by turning the hex-head screw to an engine speed of 800 rpm in neutral. d. Remove the jumper wire and reinstall the connector to the fast idle solenoid. 6. Disconnect and remove the tachometer.

1. Set the parking brake and block the drive wheels. FUEL SHUT-

90° ELBOW

FUEL RETURN LINE

SOLENOID — FAST IDLE

OFF SOLENOID SLOW IDLE ADJUSTMENT

=e

.

85772054

“| Fig. 97 350 diesel injection pump showing idle speed screws

85772055

Fig. 58 379(6.2L) diesel injection pump showing idle adjustments

ENGINE ELECTRICAL ALTERNATOR 3-5 BATTERY 3-9 DISTRIBUTOR 3-4 HEI IGNITION COIL 3-2 HEI IGNITION PICKUP COIL 3-2 IGNITION MODULE 3-3 REGULATOR 3-9 SENDING UNITS AND SENSORS 3-17 STARTER 3-10 ENGINE MECHANICAL AUXILIARY COOLING FAN 3-44 BLOCK HEATER 3-74 CAMSHAFT 3-63 CAMSHAFT BEARINGS 3-66 CHECKING ENGINE COMPRESSION 3-19 CRANKSHAFT AND MAIN BEARINGS 3-77 CYLINDER HEAD 3-46 DESIGN 3-17 ENGINE 3-30 ENGINE FAN AND CLUTCH 3-42 ENGINE OVERHAUL TIPS 3-18 EXHAUST MANIFOLD 3-40 FLYWHEEL AND RING GEAR 3-80 FREEZE PLUGS 3-73 INTAKE MANIFOLD 3-35 MAIN BEARING 3-79 OIL PAN 3-55 OIL PUMP 3-56 PISTONS AND CONNECTING RODS 3-67 RADIATOR 3-42 REAR MAIN OIL SEAL 3-75 ROCKER ARMS 3-32 THERMOSTAT 3-35 TIMING CHAIN AND SPROCKETS 3-62 TIMING CHAIN COVER AND FRONT OIL SEAL 3-56 TIMING GEARS 3-60 VALVE COVER(S) 3-31 VALVE GUIDES 3-53 VALVE LASH ADJUSTMENT 3-33 VALVE LIFTERS 3-53 VALVES & SPRINGS 3-50 WATER PUMP. 3-45 EXHAUST SYSTEM CATALYTIC CONVERTER 3-80 SYSTEM COMPONENTS 3-81 SPECIFICATIONS CHARTS ALTERNATOR AND REGULATOR SPECIFICATIONS 3-10 CAMSHAFT SPECIFICATIONS 3-24 CRANKSHAFT AND CONNECTING ROD SPECIFICATIONS 3-25 ENGINE TORQUE SPECIFICATIONS 3-30

GENERAL ENGINE SPECIFICATIONS 3-21 PISTON AND RING SPECIFICATIONS 3-26 STARTER SPECIFICATIONS 3-17 TORQUE SPECIFICATIONS 3-83 VALVE SPECIFICATIONS 3-23

aCe AND ai\li\s REBUILDING ENGINE ELECTRICAL ENGINE MECHANICAL EXHAUST SYSTEM SPECIFICATIONS CHARTS

3-2 3-17 3-80 3-10

ENGINE AND ENGINE REBUILDING

3-2

8. Clean with soft cloth and inspect cap for defects.

HEI Ignition Coil

9. Assemble new coil and cover to cap; in reverse order.

» See Figures 1, 2 and 3

HEI Ignition Pickup Coil

TESTING Bk

TESTING

1. Detach wiring connector from cap. 2. Turn four latches using a screwdriver and remove cap and coil assembly from lower housing. 3. Connect an ohmmeter between distributor cap terminals

| | :

eee tec! ain onmimearDetect the carbon DuUTON In Beeyendithe GRD. teiminalennme cistibutor cap to test eect yOkaead your fading. ea b.oe Connect an ohmmeter between the carbon button in the cap and the ‘BAT’ terminal on the distributor cap to test

ere

ered Coll Rec Oie Our feading.

c. If infinite ohms or resistance was measured in both the ignition coil is defective and needs to

measurements,

be

coll

dees

:

5. To check for an open or defective pickup coil, connect

reading between 500 and 1,500 Q should be measured. the pickup coil is defective and must be replaced.

If not

6. If the distributor has a vacuum advance unit, repeat the previous step while applying a vacuum to the vacuum unit. If a vacuum source is not available move the vacuum unit arm

with a screwdriver. Observe the ohmmeter while applying vac-

+, _.REMOVAL & INSTALLATION Es

4. To check for a shorted pickup coil, connect an ohmmeter between the distributor body (case) and one of the pickup coil measured, if resistance infinite leads.the Athereading must bebe replaced. and should is shorted pickupofcoil not

an ohmmeter between the two pickup coil leads. A steady

+ spcced + iti ; 5. it the ignition coil tests ok, it's a good idea to test the

i

1. Detach wiring connector from the distributor cap. 2. Turn four latches using a screwdriver and remove cap

and coil assembly from the distributor housing. 3. On all distributors, including distributors with Hall Effect remove rotor and disconnect the pickup coil leads from Switch, ignition module.

TACH' and ‘BAT’ to test the ignition coil’s primary coll. Eeading should be O— 1 ohm. If nol; replace coll. Batece neg oloving ohininatel: measurements Using 8 high resistance scale:

BLP

|

Replace cap, if needed.

PN

es

th

The integral ignition coil may be removed with the distributor

COIL AND CAP

ASSEMBLY

e

5

TERMINALS

cap installed in the vehicle or with the cap removed for easy access. If the coil is removed with the cap still installed on the distributor, some of the below steps may be skipped as noted. 1. Disconnect the negative battery cable. A 2. Remove the ignition wire set retainer from the top of the distributor cap. If the cap is being removed from the vehicle, keep the spark plug wires attached to the retainer for ease of installation. e>lf distributor is not equipped with a spark plug wire set retainer, it will be less hassle to remove the coil while the cap is still installed in the vehicle. If the cap must be removed, the spark plug wires should be tagged to assure proper installation. 3. If the cap is being removed from the vehicle, disconnect

the feed and module terminal wire connectors from the

4 TERMINAL

CONNECTOR

CONNECTOR

distributor cap. 4. If the cap is being removed, release the four latches by depressing and turning using a screwdriver, then remove cap and coil assembly from the distributor housing. 5. Remove ignition coil cover attaching screws and lift the cover off the distributor cap. 6. Remove ignition coil attaching screws. Using a pair of needle nose pliers, carefully lift the coil with leads from the

(DISCONNECTED FROM CAP)

end of the cap.

7. Remove the ignition coil assembly from the cap, then remove the arc seal.

ae aa Fig. 1 ‘Coil in Cap‘ Distributor

ENGINE AND ENGINE REBUILDING

3-3

2. Detach the wiring connector from the cap. 3. Turn four latches using a screwdriver and remove cap and coil assembly from the distributor housing. 4. On all distributors, including distributors with Hall Effect Switch, remove rotor and disconnect the pickup coil leads from ignition module. 5. Mark distributor shaft and gear so they can be reassembled in same position. 6. Drive out roll pin. 7, Remove gear and pull shaft assembly from distributor. 8. Remove three attaching screws and remove magnetic shield. 9. Remove retaining ring, pickup coil, magnet and pole. piece. 10. Installation is the reverse of the removal procedure.

Ignition Module » See Figure 4

TESTING The ignition module can only be tested using an ignition module tester. Since these testers are not readily available to the average do-it yourselfer, if you suspect that the ignition module is bad, its a good idea to check all the other components of the HEI system before replacing the module. Pay particular attention to all the wiring connections, since many times these connections vibrate loose or corrode. What looks

OHMMETER 85773002

like a good connection may not be, so be sure to clean alt

connections and disconnect and reconnect all connections.

REMOVAL & INSTALLATION 1. Disconnect the negative battery cable. 2. Remove the distributor cap and rotor as previously outlined in this Section. 3. Remove two module attaching.ge rews, and capacitor attaching screw. Lift module, capacitor art@ | harness assembly

from the base.

Fig. 3 Ignition coil attaching screws

+ Sea

4. Disconnect wiring harness from modules, Ifaccess is diffi-

85773003

cult, the module assembly may by pivoted upWards as the

if

harness allows. i To install: uum or moving vacuum unit arm. A reading between 500 and *,” ~ 1,500 Q should be measured. If not the pickup coil is defective and should be replaced.

->Ohmmeter may deflect if operating vacuum unit causes teeth to align. This is not a defect.

REMOVAL & INSTALLATION

Se

se) 5. Install module, wiring harness, and capacitor assembly.

Use silicone dielectric lubricant on housing under module.

a

“

Wi)

we

Failure to use the silicone dielectric lubricant on the ignition module will drastically shorten the ignition module’s life...

my

he

1. Disconnect the negative battery cable.

6 7. ‘Install ‘the distributor cap and wires. 8 vy }

Urge

3-4

ENGINE AND ENGINE REBUILDING

LUBRICANT HERE

85773152

85773004

Fig. 4 Module removed

Fig. 6 Once the bolt is loosened, the hold-down clamp may be removed from the top of the intake manifold

DYES taleley cole » See Figures 5, 6 and 7

REMOVAL |

During the distributor removal and installation proce-

dure, it is essential that the engine is NOT rotated or | ~*“ignition timing will be completely lost. If the engine is | rotated, refer to the engine position disturbed procedure to | set the engine and ignition to Top Dead Center (TDC) ___ before installation. } syria

TSE

q } —

1. Disconnect. the negative battery cable. ; 2. Release the locktabs using a small prytool, then carefully disconnect the wiring harness connectors from the side of the *

|

distributor cap. __ 3. Remove the distributor cap and wiring harness assembly from the distributor and lay it aside. If the wires are run too tightly to reposition the cap all or some of the wires may be disconnected to provide additional clearance. Be sure to tag any wires before they are removed from the cap or retainer. 4. lf equipped, disconnect the vacuum advance line. 5. Scribe a mark on the engine and distributor body in line with the rotor. Also note the approximate position of the vacuum advance unit in relation to the engine. 6. Remove the distributor hold-down clamp and nut.

Fig. 7 When removing distributor assembly, remove the round distributor gasket and keep with the distributor 7. Lift the distributor straight upward until the lower journal boss and gear clear the intake manifold, then the distributor may be tilted slightly and removed from the engine.

INSTALLATION Engine Not Disturbed 1. Carefully insert the distributor straight downward and into the engine. During installation, make sure to align the rotor to the previd@sly made marks on the housing and the engine block. The rotor may have to be turned slightly prior to installation to comgpensate the rotation during installation. as onde distributor is in place, confirm that all mating marks made during the removal procedure are in alignment. 3. Install the retaining clamp and bolt and secure in place. 4. Install the distributor cap and wiring. 5. Connect the negative battery cable, then start the

engine. 6. Check and adjust the ignition timing, then if equipped,

__connect the vacuum hose.

Engine Position Disturbed 85773151

Fig. 5 The distributor hold-down clamp bolt may be loosened using a wrench or a ratchet and crow’s foot socket

1. Turn the engine so that No. 1 piston is at the top of its compression stroke. This may be determined by covering the No. 1 spark plug hole with your thumb and rotating the engine. When the timing mark on the crankshaft pulley aligns with 0

ENGINE AND ENGINE REBUILDING on the timing scale and your thumb is pushed out by compression, No. 1 piston is at top dead center (TDC). eAn alternate method of determining No. 1 TDC is by removing the valve cover and watching the No. 1 cylinder valves as the timing mark approaches the 0 mark on the scale. If the any of the valves open while the engine is being rotated, then the No. 1 piston is on it’s exhaust stroke and the engine must be turned 360 degrees for No. 1 TDC. If the valves remain closed as the mark approaches 0, then the piston is on it’s compression stroke and is approaching TDC.

2. Position the distributor so that the vacuum advance unit points in the correct direction. Turn the rotor so that it will point to the No. 1 terminal on the distributor cap. 3. Install the distributor into the engine block. It may be necessary to turn the rotor a little in either direction in order to engage the gears. 4. Rotate the engine slightly to ensure that the oil pump shaft is mated to the distributor shaft. 5. Rotate the crankshaft 2 turns in order to bring the No. 1 piston to TDC again and check to see that the rotor is still pointing toward the No. 1 terminal of the cap. 6. After correct positioning is assured, tighten the retaining clamp. 7. Install the cap and connect the primary wire harness. Connect the negative battery cable. 8. Check the ignition timing and, if equipped, connect the vacuum hose.

Alternator

OPERATION _ » See Figures 8 and 9 Two types of alternators are used on General Motors trucks; the S| Delcotron series with 2 terminal integral regulator and the CS-130 Delcciron series with the 4 terminal integral regulator. The alternator charging system is a negative (-) ground system which consists of an alternator, a regulator, a charge indicator, a storage battery and wiring connecting the components, and fuse link wire. The alternator is belt-driven from the engine. Energgis supplied from the alternator/regulator system to the rotating field through two brushes to two slip-rings. The slip-rings are mounted on the rotor shaft and are connected to the field coil. This energy supplied to the rotating field from the battery is called excitation current and is used to initially energize the field to begin the generation of electricity. Once the alternator starts to generate electricity, the excitation current comes from its own output rather than the battery.

The alternator produces power in the form of atematitc current. The alternating current is rectified by the rectifier diode bridge into direct current. The direct current is used to charge the battery and power the rest of the electrical systems on the vehicle. When the ignition key is turned on, current flows from the battery, through the charging system indicator light on the instrument panel, to the voltage regulator, and to the alternator. nO

3-5

Since the alternator is not producing any current, the alternator warning light comes on. When the engine is started, the alternator begins to produce current and turns the alternator light off. When the alternator is operating it recharges the battery and supplies power to the electrical systems of the vehicle. All charging systems require a control circuit to limit or regulate the alternators output because as the alternator speed changes so will the output. Without a voltage regulator the alternator would overcharge the battery when engine rom was high and at low engine rpm insufficient supply would cause the battery to undercharged and some accessories would not operate at all. The voltage regulator monitors the battery’s voltage and regulates the alternator’s field current to control the alternator’s output voltage. Most solid state voltage regulators also contain a temperature compensation circuit since ambient temperature will also effect battery charge. The battery is connected to the alternator at all times, whether the ignition key is turned on or not. If the battery were shorted to ground, the alternator would also be shorted. This

would damage the alternator. To prevent this, a fuse link is installed in the wiring between the battery and the alternator. If the battery is shorted, the fuse link is melted to protect the alternator.

ALTERNATOR PRECAUTIONS To prevent damage to the alternator and regulator, the following precautionary measures must be taken when working with the electrical system. 1. Never reverse the battery connections. Always check the battery polarity visually. This is to be done before any connections are made to ensure that all of the connections correspond to the battery ground polarity of the car. 2. Booster batteries must be connected properly. Make sure the positive cable of the booster battery is connected to the positive terminal of the battery which is getting the boost. 3. Disconnect the battery cables before using a fast charger; the charger has a tendency to force current through the diodes in the opposite direction for which they were designed. 4. Never use a fast charger as a booster for starting the Car. 5. Never disconnect the voltage regulator while the engine is running, unless instructed in the testing procedures. 6. Do not ground the alternator output terminal. 7. Do not operate the alternator on an open circuit with the field energized. 8. Do not attempt to polarize the alternator. 9. Disconnect the battery cables and remove the alternator before using an electric arc welder on the car. 10. Protect the alternator from excessive moisture. If the engine is to be steam cleaned, cover or remove the alternator.

TESTING Preliminary Charging System Tests 1. If you suspect a defect in your charging system, first perform these general checks before going on to more specific tests.

Te

*

3-6

ENGINE AND ENGINE REBUILDING Delcotron ‘SI‘ Series Alternator

» See Figure 10 ->Delcotron ‘SI alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron ‘CS‘ alternators are identified by having a four terminal integral voltage regulator connector on the alternator.

CHARGING SYSTEM STATIC TEST 1. Disconnect the two terminal connector at the alternator. 2. With the ignition on, connect a voltmeter between the

51. 52. 53. 54.

“BAT” No. 1 No. 2 Field

Terminal Terminal Terminal Ground Hole 85773147

alternator’s harness connector terminal 1(brown wire) and ground. e If 10 volts or greater is measured go to the next step. e If no voltage is measured, repair the short to ground in the wiring between the generator light in the instrument panel and the alternator connector. 3. With the ignition on, connect a voltmeter between the alternators harness connector terminal 2 (red wire) and ground. e If 10 volts or greater is measured, go to the next step. : e If no voltage is measured, repair the open or short to ground in the wire between the alternator and the fusible link at the starter solenoid. 4. Measure voltage at the alternator between the ‘BAT’ ring terminal and ground. e If 10 volts or greater is measured, perform the alternator output test.

Fig. 8 ‘SI‘ series alternator

e If no voltage is measured, repair the open in the wiring.

ALTERNATOR OUTPUT TEST This test can only be performed on Delcotron ‘SI* type alternators which have the alternator field ground tab test hole. This test cannot be performed on the Delcotron ‘CS' type alternators. An ammeter is required to perform this test.

=>Deicotron ‘SI‘ alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron ‘CS‘ alternators are identified by having a four tefmi- nal integral voltage regulator connector on the alternator.

51. BAT Terminal 55. Terminals PL, 1,S 85773148

Fig. 9 ‘CS‘ series alternator 2. Check the condition of the alternator belt and tighten it if necessary. 3. Clean the battery cable connections at the battery. Make - gure the connections between the battery wires and the battery _ Clamps are good. 4. Test the battery cables as outlined in Section 1. 5. Check the charging system wiring for any obvious breaks or shorts. 6. Check the battery to make sure it is fully charged and in good condition. 7. If all the previous checks were ok, proceed to the applicable test.

1. Disconnect the negative battery cable. 2. Disconnect the battery terminal on the alternator. 3. Connect the ammeter’s negative lead to the battery wire disconnected in the previous step. 4. Reconnect the negative battery cable and turn on all lights and accessories. Leave the lights and accessories on for a minute or two to draw down the battery a little before going on to the next step. 5. Start the engine and run it until you obtain a maximum current reading on the ammeter. Make sure all accessories are on blower motor, wipers, air conditioning, high beam headlights, etc. Record the reading and compare to the alternator’s” rated output, which is stamped onto the frame of the alternator. If the reading is: e Within 10 percent of the rated output, the alternator is good. ¢ Not within 10 percent of the rated output go to the next step.

6. With the engine running at moderate speed and all accessories on, ground the alternator field. This can be done by

ENGINE AND ENGINE REBUILDING

3-7

3. With the ignition on, connect a voltmeter between the alternator’s harness connector terminal ‘I' (red or pink wire) and ground. e If 10 volts or greater is measured, go to the next

step.

e If no voltage is measured, repair the open or short to ground in the wire between the alternator and the fusible link at the starter solenoid. 4. Measure voltage at the alternator between the ‘BAT’ ring terminal and ground. e If 10 volts or greater is measured, the problem is in the alternator. Remove the alternator for repair or replacement. e If no voltage is measured, repair the open in the wiring.

=

7

a eee cata Ve

REMOVAL & INSTALLATION b See Figures 12, 13, 14, 15, 16, 17, 18, 19, 20 and 21

1. Disconnect negative battery cable, then disconnect the positive cable from the battery. 2. Disconnect and tag all wiring to the alternator. 3. If necessary for removal clearance, disconnect the ground strap from the alternator bracket. 4. If equipped, remove the alternator brace bolt. 5. If the truck is equipped with power steering, it may be necessary to loosen the pump brace and mount nuts.

RECTIFIER

85773149

Fig. 10 ‘SI series alternator schematic inserting a insulated screwdriver in the alternator field test hole and allowing the screwdriver shaft to touch the alternator case. Again record the reading and compare to the alternator’s rated output, which is stamped onto the frame of the alternator. If the reading is: e Within 10 percent of the rated output, the alternator’s regulator is most likely defective. e Not within 10 percent of the rated output, the problem is with either the alternator’s field winding, diode trio, rectifier bridge*or stator.

6. Remove the lower mounting bolt, then support the alter-

nator and remove the upper mounting/adjusting bolt. 7. Slip the alternator belt from the pulley and remove the alternator from the truck. SWITCH

INDICATOR LAMP 9

BATTERY

RESISTOR

Delcotron ‘CS‘ Generators

=>Delcotron ‘SI‘ alternators can be identified by having a two terminal integral voltage regulator connector. Delcotron ‘CS‘ alternators are identified by having a four terminal integral voltage regulator connector on the alternator. 1. Disconnect the four terminal connector-at the alternator. 2. With the ignition on, connect a voltmeter between the alternator’s harness connector terminal ‘L‘ (brown wire) and ground. e If 10 volts or greater is measured go to the next step. e If no voltage is measured, repair the short to ground

in the wiring between the generator light in the instrument

>

REGULATOR =| o

e

0000000004 FIELD

Sec

RECTIFIER BRIDGE

panel and the alternator connector.

See Figures 22 and 23

°K CAUTION Never operate the starter motor than 30 seconds at a time without pausing to allow it to cool for at least two minutes. Overheating, caused by excessive cranking, will seriously damage the starter motor.

Basic starter testing can be done without tools. The problem is a bad battery and a defective starter cause the same symptoms. First test and charge the battery to confirm it is in good condition. 1. Place a voltmeter across the battery and try to start the Car. 2. If the starter makes no sounds and the voltmeter didn’t move in the last step, the wires from the ignition switch to the Starter need to be checked. Check for 12 volts by connecting

ENGINE AND ENGINE REBUILDING

PLUNGER

ORIVE GEAR HOUSING

RETURN SPRING

SOLENOID END FRAME INSULATOR

COMMUTATOR END FRAME

FIBER

WASHER

RETAINER

CLUTCH

AND

DRIVE ASM.

FIELD

FRAME

CENTER

ARMATURE

BEARING

85773017

Fig. 22 Exploded view of the 20MT starter motor used on the 350 diesel. Gasoline engine starters similar

SWITCH TERMINAL

SOLENOID PLUNGER

Wey,

1, Tm

hl

RETURN SPRING

il

a)

mhary

(oe

i USHING

i”a PINION STOP

INSULATED BRUSH ee

GROUNDED BRUSH HOLDER RISER BARS

CONDUCTORS TO RISER BARS

OVERRUNNING CLUTCH

TO ARMATURE

85773018

Fig. 23 Cross-Section of 10MT starter motor

3-11

3-12

ENGINE AND ENGINE REBUILDING

a voltmeter between the starter solenoid’s small gauge (little) wire and ground while the ignition is turned to start. — e |f 10 volts or more is measured, the problem is most . likely the open starter solenoid. is not the problem the e If no voltage is measured, or wiring to switch safety neutral switch, ignition starter but the the starter. e If less than 10 volts is measured but some voltage is measured, check the battery and the battery cables. 3. If the starter clicks, and the voltmeter moves very little. Check the solenoid, battery cables and wire connections. 4. If the engine cranks very slow or seems to jam and the battery and battery cables are ok, the starter is the probable problem. 5. If the vehicle is hard to crank warm, but after given time to cool cranks easier. The starter is the probable problem. 6. Before condeming the starter always check the engine mechanical condition. A good starter can not crank over a damaged engine, or engine that has been extremely overheated, is low on oil, has extremely thick and dirty oil.

Fig. 25 Support the starter by hand and withdraw the mounting bolts 6. On engines with a solenoid heat shield, remove the front bracket upper bolt and detach the bracket from the starter.

» See Figures 24, 25, 26 and 27

The starter assembly is very heavy. Be careful to fully support the assembly when removing the mounting bolts. The assembly is heavy enough to cause injury, especially if it should fall on your head when the last mounting bolt is loosened.

The following is a general procedure for all trucks, and may vary slightly depending on model and series.

2 mounting bolts. Lower the starter front end first, and then

REMOVAL & INSTALLATION

>The starters on some engines require the addition of shims to provide proper clearance between the starter pinion gear and the flywheel. The shims are available in 0.015 inch sizes from General Motors dealers. 1. Disconnect the battery ground cable. 2. Raise and support the vehicle with jackstands. 3. Disconnect and tag all wires at the solenoid terminals. e>Sometimes, the wire fasteners may be extremely difficult to reach with the starter installed. If the wires cannot be disconnected, wait until the starter bolts and removed and the starter can be lowered slightly for better access, but

do not allow the starter to hang by the wires or they could be damaged. 4. Reinstall all nuts as soon as they are removed, since the thread sizes are different. 5. If equipped, remove the mounting bracket nuts or bolts, as applicable.

7. Support the starter by hand, then loosen and remove the remove the unit from the truck. If any shims were installed between the starter and the engine block, note the size and location of the shims to assure proper installation. 8. Reverse the removal procedures to install the starter. If any shims were present, be sure to reposition them as noted during removal in order to assure proper starter operation. Torque the two mounting bolts to 25-35 ft. Ibs. Shimming the Starter

» See Figures 28, 29 and 30 Starter noise during cranking and after the engine fires is often a result of too much or too little distance between the starter pinion gear and the flywheel. A high pitched whine during cranking (before the engine fires) can be caused by the pinion and flywheel being too far apart. Likewise, a whine after the engine starts (as the key is released) is often a result of the pinion-flywheel relationship being too close. In both cases flywheel damage can occur. Shims are available in 0.015 inch

85773165 85773157

Fig. 24 Loosen the nuts retaining the starter solenoid wires and disconnect the harness

Fig. 26 If necessary, the starter may be lowered slightly for access to disconnect the solenoid wires. If this is done, be careful not to stretch or damage the wiring

ENGINE AND ENGINE REBUILDING

3-13

0.015 inch at this location will decrease the clearance about 0.010 inch.

STARTER SOLENOID REPLACEMENT 1. Disconnect the negative battery cable. 2. Remove the starter from the vehicle. 3. Remove the screw and washer from the field strap terminal. 4. Remove the two solenoid-to-housing retaining screws and the motor terminal bolt. 5, Remove the solenoid by twisting the unit 90 degrees. 6. To replace the solenoid, reverse the above procedure. Make sure the return spring is on the plunger, and rotate the solenoid unit into place on the starter.

STARTER DRIVE REPLACEMENT » See Figures 31, 32, 33 and 34 1. Disconnect the negative battery cable. 2. Remove the starter from the vehicle. 3. Disconnect the field coil straps from the solenoid. 4. Remove the through-bolts (usually 2), and separate the commutator end frame, field frame assembly, drive housing, and armature assembly from each other. 85773011

Fig. 27 Starter mountings sizes to properly adjust the starter on its mount. You will also need a flywheel turning tool, available at most auto parts stores or from any auto tool store. If your car’s starter emits the above noises, follow the shimming procedure below: 1. Disconnect the negative battery cable. 2. Remove the flywheel inspection cover on the bottom of the bellhousing. 3. Using the flywheel turning tool, turn the flywheel and examine the flywheel teeth. If damage is evident, the flywheel should be replaced. 4. Insert a screwdriver into the small hole in the bottom of the starter and move the starter pinion and clutch assembly so the pinion and flywheel teeth mesh. If necessary, rotate the flywheel so that a pinion tooth is directly in the center of the two flywheel teeth and on the centerline of the two gears, as shown in the accompanying illustration. 5. Check the pinion-to-flywheel clearance by using a 0.020 inch wire gauge (a spark plug wire gauge may work here, or you can make your own). Make sure you center the pinion tooth between the flywheel teeth and the gauge, NOT in the corners, as you may get a false reading. If the clearance is under this minimum, shim the starter away from the flywheel by adding shim(s) one at a time to the starter mount. Check clearance after adding each shim. 6. If the clearance is a more than 0.050 inch, shim the starter towards the flywheel. Broken or severely mangled flywheel teeth are also a good indicator that the clearance here is too great. Shimming the starter towards the flywheel is done by adding shims to the outboard starter mounting pad only.

Check the clearance after each shim is added. A shim of

>On the diesel starters, remove the insulator from the end frame. The armature on the diesel starter remains in the drive end frame.

5. On diesel starters, remove the shift lever pivot bolt. On the diesel 25 MT starter only, remove the center bearing screws and remove the drive gear housing from the armature shaft. The shift lever and plunger assembly will now fall away from the starter clutch. 6. Slide the two-piece thrust collar off the end of the armature shaft. 7. Slide a %s inch deep socket, piece of pipe or an old pinion onto the shaft so that the end of the pipe, socket, or pinion butts up against the edge of the pinion retainer. 8. Place the lower end of the armature securely on a soft surface, such as a wooden block or thick piece of foam rubber. Tap the end of the socket, pipe or pinion, driving the retainer towards the armature end of the snapring. 9. Remove the snapring from the groove in the armature shaft with a pair of pliers. If the snapring is distorted, replace it with a new one during reassembly. Slide the retainer and starter drive from the shaft; on diesel starters, remove the fiber washer and the center bearing from the armature shaft. On gasoline engine starters, the shift lever and plunger may be disassembled at this time, if necessary by removing the roll pin. 10. To assemble, lubricate the drive end of the armature shaft with silicone lubricant. On diesel starters, install the

center bearing with the bearing toward the armature winding, then install the fiber washer on the armature shaft. 11. Slide the starter drive onto the armature shaft with the pinion facing outward (away from the armature). Slide the retainer onto the shaft with the cupped surface facing outward.

314

ENGINE AND ENGINE. REBUILDING . Use shims as required FRONT

. Shield

OF

Starter-Noise Diagnostic Procedure 1. Starter noise during cranking: remove 1—.015" double shim or add single .015” shim to outer bolt only. 2. High pitched whine after engine fires: add .015" double shims until noise disappears. See text for complete procedure.

85773012

Yp PARMATURE

Ay Rust

FIBER SHAFT _ WASHER _7 WASHER RETAINER

:|Y 6) Bib

Pa CENTER BEARING

SUGGESTED WIRE GAUGE

Were SNAP

ie

CLUTCH AND DRIVE

85773013

Fig. 29 Flywheel to pinion clearance check

RING

ASSEMBLY 85773016

Fig. 31 Starter drive assembly removed

A .015” SHIM WILL INCREASE THE CLEARANCE APPROXIMATELY .005”. MORE THAN ONE SHIM MAY BE REQUIRED.

SCREW DRIVER

85773019 85773014

Fig. 30 Meshing starter teeth —

Fig. 32 Use a piece of pipe or and old socket to drive the retainer toward the snapring

ENGINE AND ENGINE REBUILDING 3-15 15. Engage the shift lever yoke with the clutch. Position the front of the armature shaft into the bushing, then slide the

complete drive assembly into the drive gear housing.

e>On non-diesel starters the shift lever may be installed in the drive gear housing first. 16. On the 25 MT diesel starter only, install the center bear-

85773020

SHIFT LEVER PIVOT BOLT

ing screws and the shift lever pivot bolt, and tighten securely. 17. Apply a sealing compound approved for this application onto the drive housing, to the solenoid flange where the field frame contacts it. Position the field frame around the armature shaft and against the drive housing. Work carefully and slowly to prevent damaging the starter brushes. 18. Lubricate the bushing in the commutator end frame with a silicone lubricant, place the leather washer onto the armature shaft, and then slide the commutator end frame over the shaft and into position against the field frame. On diesel starters, install the insulator and then the end frame onto the shaft.

Line up the bolt holes, then install and tighten the throughbolts. Make sure they pass through the bolt holes in the insulator. 19. Connect the field coil straps to the motor terminal of the

F

solenoid. If replacement of the.starter drive fails to cure improper ORIVE GEAR HOUSING 85773021

Fig. 34 Removing shift lever and plunger from starter

engagements of the starter pinion be defective parts in the solenoid procedure is to take the assembly clearance check can be made by

to the flywheel, there may and/or shift: lever. The best to a shop where a pinion energizing the solenoid on a

test bench. If the pinion clearance check can be made by energizing the solenoid on a test bench. If the pinion clearance

12. Again support the armature on a soft surface, with the pinion on the upper end. Center the snapring on the top of the shaft. Use a new ring if the old one was misshapen or damaged. Gently place a block of wood on top of the snapring so as not to move it from a centered position. Tap the wooden block with a hammer in order to force the snapring around the shaft. Slide the ring down into the snap groove. 13. Lay the armature down flat on your work surface. Slide the retainer close up onto the shaft and position it and the thrust collar next to the snapring. Using two pairs. of pliers on opposite ends of the shaft, squeeze the thrust collar and the retainer together until the snapring is forced into the retainer. 14. Lube the drive housing bushing with a silicone lubricant.

is incorrect, disassemble the solenoid and shift lever, inspect, and replace the worn parts.

STARTER BRUSH REPLACEMENT 1. Disassemble the starter by following Steps 1 and 2 of the Drive Replacement procedure above. #7” 2. Replace the brushes one at a time to avoid having to es mark the wiring. For’each: brush: rémove the brush holding “a screw; remove the old brush and position the new brush in the same direction (large end toward center of field frame), position the wire connector on top of the brush, line up the holes, and reinstall the screw. Make sure the screw is: snug une

to ensure good contact. 3. Reassemble starter according to Steps 8-17 above.

Sov iad

“

3-16

ENGINE AND ENGINE REBUILDING Troubleshooting Basic Starting System Problems

Starter motor rotates engine slowly

Solution

Cause

Problem

- Battery charge low or battery

- Charge or replace battery

defective

- Defective circuit between battery

- Clean and tighten, or replace

and starter motor - Low load current

- Bench-test starter motor. Inspect

cables for worn brushes and weak

brush springs. * High load current

- Bench-test starter motor. Check

engine for friction, drag or coolant in cylinders. Check ring gear-topinion gear clearance. Starter motor will not rotate engine

- Battery charge low or battery defective - Faulty solenoid

- Charge or replace battery

* Damage drive pinion gear or ring gear » Starter motor engagement weak * Starter motor rotates slowly with high load current

- Replace damaged gear(s)

+ Check solenoid ground. Repair or

replace as necessary.

- Engine seized

Starter motor drive will not engage (solenoid known to be good)

- Defective contact point assembly * Inadequate contact point assembly ground * Defective hold-in coil

Starter motor drive will not

- Bench-test starter motor * Inspect drive yoke pull-down and point gap, check for worn end bushings, check ring gear clearance * Repair engine » Repair or replace contact point assembly > Repair connection at ground screw

- Replace field winding assembly

+ Starter motor loose on flywheel housing * Worn drive end busing - Damaged ring gear teeth > Drive yoke return spring broken or missing

* Tighten mounting bolts

Starter motor drive disengages prematurely

* Weak drive assembly thrust spring * Hold-in coil defective

* Replace drive mechanism - Replace field winding assembly

Low load current

- Worn brushes * Weak brush springs

: Replace brushes - Replace springs

disengage

- Replace bushing - Replace ring gear or driveplate - Replace spring

8577305C

ENGINE AND ENGINE REBUILDING

3-17

SSS

STARTER SPECIFICATIONS Starter © Year

Identification

1980-82

1108778 ®

1983-86

|

No Load Test Amps oO)

Volts

eT

sl

ae

rpm

Sa

5500-10,500

1187780 1109056 © 1109052 11087760

9 9 9 9

3500-6000 5500-10,500 7500-10,500 7500-10,500

1109561

g

1109535 1998241

9 10

6000-11,900

1987

7500-10,500

45-70

10

60-85 65-95

10 10

70-110 120-210

7000-11,900 7500-10,500 6800-10,500 7500-10,500

6500-10,700

|

6500-10,700 9000-13,400

9000-13, 400 9000-13,400

6500-10,700 6500-10,700 6500-10,700 6500-10,700 ® Solenoid included @® ‘‘R”' terminal removed ® Brush spring tension is 35 oz. for all starters.

Lock testisnot recommended. 85773c15

Sending Units and Sensors REMOVAL & INSTALLATION

3. Remove the sensor using a deep well socket or Kent Moore tool J-21757. 4. To install the sensor, follow the previous*steps in reverse order.

Coolant Temperature Sender Oil Pressure

1. Disconnect the negative battery cable from the battery. 2. Disconnect the wiring harness connector from the oil pressure sending unit. The sending unit can be found: e On in-line six cylinder engines, the sensor is located in the engine block above the starter. e On V6 and V8 (except 454 engines) engines the sensor is located near the left front side of the distributor. e On V8 454 engines, the sensor is located at the rear left side of the engine block. e On diesel engines, the sensor is located above the flywheel housing on the left side of the engine block.

ENGINE MECHANICAL

All Chevrolet and GMC truck engines, whether 6 cylinder or V8, are water-cooled, overhead valve powerplants. All engines

use cast iron cylinder blocks and heads. The 6-250 and 6-292 in-line engines are all very similar in design although some 6-250s have an integral cylinder head

1. Disconnect the negative battery cable from the battery. 2. Loosen the radiator cap to relieve pressure in the cooling system and then retighten the cap. This will also help minimize the amount of coolant lost when replacing the sender. 3, Disconnect the wiring harness connector from the coolant temperature sending unit. 4. Have the replacement sender or a cork handy to help minimize coolant loss before removing the sending unit. Remove the sending unit. 5. To install the sensor follow the previous steps in the reverse order. 6. Check coolant level and refill as necessary.

| and intake manifold. Crankshafts are supported in seven main bearings, with the thrust taken by No. 7. The camshaft is low in the block and driven by the crankshaft gear; no timing chain is used. Relatively long pushrods actuate the valve through ball jointed rocker arms. The small block family of engines, which includes the 8-283, 8-305, 8-307, 8-327, 8-350, and 8-400 blocks, have all sprung from the basic design of the 1955 265 cu. in. engine. It was

3-18

ENGINE AND ENGINE REBUILDING

this engine that introduced the ball joint rocker arm design which is now used by many car makers. This line of engines features a great deal of interchangeability, and later parts may be utilized on earlier engines for increased reliability and/or performance. The Chevrolet built V6 262 cu. in. engine introduced in 1986 evolved from the small block V8 family of engines and share many of the same parts. The 8-396, 8-402, and 8-454 engines are known as the Mark IV or big blocks. These engines feature unusual cylinder heads, in that the intake and exhaust valves are canted at the angle at which their respective port enters the cylinder. The big block cylinder heads use ball joint rockers similar to those on the small block engines. Two V8 diesel engines have been available in the Chevrolet Pick-Ups since 1978. The first was the Oldsmobile built 8-350 engine which was derived from a gasoline engine of the same displacement. Internal engine components such as the crankshaft, main bearings, connecting rods, pistons, wrist pins and piston rings all are heavier made to withstand the considerably higher pressures and stresses common to diesel engines. Diesel ignition occurs because of heat developed in the combustion chamber during compression. This is the reason for the diesel’s high compression ratio (22.5:1). Because the fuel ignites under compression, the need for spark plugs and high voltage ignition is eliminated. A new V8 diesel of 379 cu. in (6.2L) was introduced for the pick-ups in 1982, superceding the 350. This engine is built by Chevrolet; GM’s Detroit Diesel Division aided in much of the engine’s design. The 379 is even stronger, component by component, than the 350. Designed ‘from the block up” as a diesel, it utilizes robust features such as four-bolt main bearing caps.

Engine Overhaul Tips Most engine overhaul procedures are fairly standard. In addition to specific parts replacement procedures and complete specifications for your individual engine, this Section also is a guide to accepted rebuilding procedures. Examples of standard rebuilding practice are shown and should be used along with specific details concerning your particular engine. Competent and accurate machine shop services will ensure maximum performance, reliability and engine life. In most instances it is more profitable for the do-it-yourself mechanic to remove, clean and inspect the component, buy the necessary parts and deliver these to a shop for actual machine work. On the other hand, much of the rebuilding work (crankshaft, block, bearings, piston rods, and other components) is well within the scope of the do-it-yourself mechanic.

TOOLS The tools required for an engine overhaul or parts replacement will depend on the depth of your involvement. With a few exceptions, they will be the tools found in a mechanic’s tool kit

(see Section 1). More in-depth work will require any or all of the following: e a dial indicator (reading in thousandths) mounted on a universal base e micrometers and telescope gauges e jaw and screw-type pullers e scraper valve spring compressor ring groove cleaner piston ring expander and compressor ridge reamer cylinder hone or glaze breaker Plastigage® e engine stand The use of most of these tools is illustrated in this Section. Many can be rented for a one-time use from a local parts jobber or tool supply house specializing in automotive work. Occasionally, the use of special tools is called for. See the information on Special Tools and Safety Notice in the front of this book before substituting another tool.

INSPECTION TECHNIQUES Procedures and specifications are given in this Section for inspecting, cleaning and assessing the wear limits of most major components. Other procedures such as Magnaflux® and Zyglo® can be used to locate material flaws and stress cracks. Magnaflux® is a magnetic process applicable only to ferrous materials. The Zyglo® process coats the material with a fluorescent dye penetrant and can be used on any material. Check for suspected surface cracks can be more readily made using spot check dye. The dye is sprayed onto the suspected area, wiped off and the area sprayed with a developer. Cracks will show up brightly.

OVERHAUL TIPS Aluminum has become extremely popular for use in engines, due to its low weight. Observe the following precautions when handling aluminum parts: e Never hot tank aluminum parts, the caustic hot tank solu-

tion will eat the aluminum. e Remove all aluminum parts (identification tag, etc.) from engine parts prior to the tanking. e Always coat threads lightly with engine oil or anti-seize compounds before installation, to prevent seizure. e Never overtorque bolts or spark plugs especially in aluminum threads. Stripped threads in any component can be repaired using any of several commercial repair kits (Heli-Coil®, Microdot®, Keenserts®, etc.). When assembling the engine, any parts that will be frictional contact must be prelubed to provide lubrication at initial startup. Any product specifically formulated for this purpose can be used, but engine oil is not recommended as a prelube. When semi-permanent (locked, but removable) installation of bolts or nuts is desired, threads should be cleaned and coated with Loctite® or other similar, commercial non-hardening sealant.

ENGINE AND ENGINE REBUILDING REPAIRING DAMAGED THREADS

3-19

Checking Engine Compression

» See Figures 35, 36, 37, 38 and 39

» See Figure 40

Several methods of repairing damaged threads are available. Heli-Coil® (shown here), Keenserts® and Microdot® are among the most widely used. All involve basically the same ‘principle — drilling out stripped threads, tapping the hole and installing a prewound insert — making welding, plugging and oversize fasteners unnecessary. Two types of thread repair inserts are usually supplied: a

A noticeable lack of engine power, excessive oil consumption and/or poor fuel mileage measured over an extended period are all indicators of internal engine war. Worn piston rings, scored or worn cylinder bores, blown head gaskets, sticking or burnt valves and worn valve seats are all possible culprits here. A check of each cylinder’s compression will help you locate the problems. As mentioned in the Tools and Equipment Section of Section 1, a screw-in type compression gauge is more accurate that the type you simply hold against the spark plug hole, although it takes slightly longer to use. It’s worth it to obtain a more accurate reading.

standard type for most Inch Coarse, Inch Fine, Metric Course

and Metric Fine thread sizes and a spark lug type to fit most spark plug port sizes. Consult the individual manufacturer's catalog to determine exact applications. Typical thread repair kits will contain a selection of prewound threaded inserts, a tap (corresponding to the outside diameter threads of the insert) and an installation tool. Spark plug inserts usually differ because they require a tap equipped with pilot threads and a combined reamer/tap Section. Most manufacturers also supply blister-packed thread repair inserts separately in addition to a master kit containing a variety of taps and inserts plus installation tools. Before effecting a repair to a threaded hole, remove any snapped, broken or damaged bolts or studs. Penetrating oil can be used to free frozen threads. The offending item can be removed with locking pliers or with a screw or stud extractor. After the hole is clear, the thread can be repaired, as shown

GASOLINE ENGINES 1. Warm up the engine to normal operating temperature. 2. Remove all the spark plugs. 3. Disconnect the high tension lead from the ignition coil. 4. On fully open the throttle either by operating the carburetor throttle linkage by hand or by having an assistant floor the accelerator pedal. 5. Screw the compression gauge into the No.1 spark plug hole until the fitting is snug.

in the series of accompanying illustrations. Be careful not to crossthread the plug hole. On aluminum cylinder heads use extra care, as the threads in these heads are easily ruined. BOLT OR SCREW

THREADED

INSERTION

sommes S

DAMAGED

ED:

THREADS

ll: 85773022

Fig. 35 Damaged bolt holes can be repaired with thread repair inserts

TANG

NOTCH

;

85773023

Fig. 36 Standard thread repair insert (left) and spark plug thread insert(right)

6. Ask an assistant to depress the accelerator pedal fully on both carbureted and fuel injected vehicles. Then, while you read the compression gauge, ask the assistant to crank the engine two or three revolutions using the ignition switch. 7. Read the compression gauge at the end of each series of cranks, and record the highest of these readings. Repeat this procedure for each of the engine’s cylinders. Compare the highest reading of each cylinder to the compression pressure specification in the Tune-Up Specifications chart in Section 2. The specifications in this chart are maximum values. A cylinders compression pressure is usually acceptable if it is not less than 80% of maximum. The difference between any two cylinders should be no more than 12-14 pounds. 8. If a cylinder is unusually low, pour a tablespoon of clean engine oil into the cylinder through the spark plug hole and repeat the compression test. If the compression comes up after adding the oil, it appears that the cylinder’s piston rings or bore are damaged or worn. If the pressure remains low, the valves may not be seating properly (a valve job is needed), or the head gasket may be blown near that cylinder. If compression in any two adjacent cylinders is low, and if the addition of oil doesn’t help the compression, there is leakage past the head gasket. Oil and coolant water in the combustion chamber can result from this problem. There may be evidence of water droplets on the engine dipstick when a head gasket has blown.

S577S024

Fig. 37 Drill out the damaged threads with specified drill. Drill completely through the hole or to the bottom of a blind hole

SSTTIOLT

Fig. 40 The screw-in type compression gauge is more accurate

85773025

Fig. 38 With the tap supplied, tap the hole to receive the thread insert. Keep the well oiled and back it out frequently to avoid clogging the threads

Fig. 41 Diesel engines require a special compression gauge adapter

DIESEL ENGINES » See Figure 41

85773026

Fig. 39 Screw the threaded insert onto the installation tool until the tang engages the slot. Screw the insert into the tapped hole until it is 1/4-1/2 turn the tang with a hammer and punch

Checking cylinder compression on diesel engines is basically the same procedure as on gasoline engines except for the following: 1. A special compression gauge adaptor suitable for diesel engines (because these engines have much greater compression pressures) must be used. 2. Remove the injector tubes and remove the injectors from each cylinder.

Don’t forget to remove the washer underneath each injector. Otherwise, it may get lost when the engine is cranked. SO

RE

3. When fitting the compression gauge adaptor to the cylinder head, make sure the bleeder of the gauge (if equipped) is closed. 4. When reinstalling the injector assemblies, install new washers underneath each injector.

a EG

ENGINE AND ENGINE REBUILDING

3-21

GENERAL ENGINE SPECIFICATIONS

Year

1980

Engine No. Cyl. Displacement (cu. in.)

Fuel System

6-250 6-250 Calif. 6-292 8-305

2 bbl 2 bbl

8-350 LD Calif.

4 bbl

8-400HD__|

4 bbI

6-250 Calif.

2 bbl 1 bbl

Advertised Horsepower @rpm =

Advertised Torque @ rpm (ft. Ibs.) =

Advertised Compression Ratio

Oil Pressure @ 2000 rpm

3.530 3.530 4.120 3.480

8.3:1 8.3:1 7.8:1 8.5:1

40-60 40-60 40-60 45

4.000 x 3.480

8.2:1

45

8.3:1 22.5:1 8.351 79:1 8.3:1

45 36 40 40 40-60

8.3:1

40-60

7.8:1 8.5:1 9.2:1

40-60 45 45

Bore and Stroke (in.)

3.870 3.870 3.870 3.740

8-350 LD

170 @ 4000

275 @ 2000

x x x x

1981 6-292 8-305 8-305

2bbl

130°@ 4000

205 @ 2000

115@3400 | 215@ 1600 | 135@4200 | 235@ 2400 155@4400 | 252 @ 2400

3.870 x 3.53 0 3.870 x 4.120 :

3.740 x 3.480 3.740 x 3.480

8.2:1

45

easoup | aon |175@4000 | 275@2400 | 4.000% 3.480 | 21 | 48 16 8.350 | Dieser |125@3600 |205@ 1600 | 4057«3.385 | 2251 | 95 «0 1082 10-60 e202 [tor] 115@3400 |215@ 1600 | 3870%4.120 | 7.81 | 40-60 40 re g-305 | bi 16 18 re Diese 15 40 10-60 1983-64 40-60 8-305 O 160@4400 | 235 @ 2000 3.740 x 3.480 8.5:1 eras 45 | P8050 _| 15 8-3050 45 8.2:1 8-3500 8.2:1 8-3500 8-379 | Diesel | 140@3600 | 240@2000 | 3980x3800 | 21.5:1 8-454

210 @ 3800

7.9:1

45 45

40

85773c03

AND ENGINE REBUILDING 3-22 ENGINE e

é

eee

|

Year 1985

GENERAL ENGINE SPECIFICATIONS

Engine No. Cyl. Displacement (cu. in.) 6-250

Fuel System 4 bbl

Advertised Horsepower @rpm«# 115 @ 3600

Advertised Torque @ rpm (ft. Ibs.) = 200 @ 2000

Bore and Stroke (in.) 4.000 x 4.000

6-292

1 bbl

115 @ 3600

215@ 1600

3.876 x 4.120

4bbi__|

160.@ 4400

Advertised

| 8-3500 | a4bbi | 165@3800 | 275@1600_ | 4.000 x 3.480_ | 83500 | bbl «| 155@4000 | 240@2800_ | 4.000 x 3.480_| 1986

1 bb

230 @3800

| 83050 | Abbi_| 150@3800_ | 240@2400 | 3.740 x 3.480_| | 83500 | Abbi | 165@3800_| 275@1600_| 4.000 x 3.800_| 240 @3800

1987

Compression Ratio 9.3:1

8.0:1 8.6:1 8.331 8.2:1

8.3:1 e107 8.0:1 8.0:1 6.337 8.5:1 9.0:1 8.3:1 8.3:1 8.0:1

9.3:1 9.0:1

240 @3800

8.5:1 8.0:1

*Starting 1972, horsepower and torque are SAE net figures. They are measured at the rear of the transmission with all accessories installed and _ operating. Since the figures vary when a given engine is installed in different models, some are representative rather than exact. EFl—Electronic Fuel Injection

® @ ® ®

375 255 250 385

@ @ @ @

2800—Calif. 2800 HD 3800—Calif. 2800—Calif.

© @ ® ® @ © © ®

Not available in California 49-states California Eng. Code F Eng. Code H Eng. Code L Eng. Code M 195 @ 4000 for GVWR over 8500 Ibs. S5778d08

ENGINE AND ENGINE REBUILDING

3-23

VALVE SPECIFICATIONS Engine No. Cyl. Displacement (cu. in.)

Year

Seat Angle (deg.)

Face Angle (deg.)

Spring Test Pressure (Ibs. @in.)

Spring Installed Height (in.) 0)

Stem to Guide Clearance (in.) Intake Exhaust

Stem Diameter (in.) Intake —_Exhaust

| 6-250 | 46 | 45 | [email protected]] 12% | 0.0010-0.0027

0.3414 |0.3414

| 8305 | 46 | 45 | [email protected] | © | 0.0010-0.0027 | 8350 | 46 [45 | [email protected] | © ‘| 0.0010-0.0027

0.3414 |0.3414 0.3414

45©

0.0010-0.0027

0.3414 |0.3414

0.0010-0.0027 |0.0012-0.0029 | 0.3414 | 0.3414

| 8454 | 46 | 45 | [email protected] | 1% | 0.0010-0.0027 8-350

151 @ 1.30 [ilies

Diesel

GUE é

| 6250 | 46 | 45 | [email protected] | 1.66 ~|0.0010-0.0027 | 6-202 | 46 | 46 | [email protected] | 1.66 _|0.0010-0.0027 | 8305 | 46 | 45 | [email protected]| 12%2 | 0.0010-0.0027 0.0010-0.0027 205 @ 1.30

1982-87

0.3719 |0.3719

0.0015-0.0032 en |

ae

0.3414 0.3414 0.3414

0.3414 0.3414 0.3414 0.3414

0.0015-0.0032 ae

_ 8454 | 46 | 45 | 200@140 | 15%os 0.3719 0.3719 | 6250 | 46 | 45 | [email protected] | 1.66 _|0.0010-0.0027 |0.0015-0.0032 |0.3414 |0.3414 0.3414 0.3414 | 6202 | 46 | 46 | [email protected] | 1.66 | 0.0010-0.0027 |0.0015-0.0032 |0.3414 0.3414 8305 | 46 | 45 | [email protected]@| 12%/0@ |0.0010-0.0027 |0.0010-0.0027 |0.3414 |0.3414 8350 | 46 | 45 | 200@1250| 12%42@ |0.0010-0.0027 |0.0010-0.0027 |0.3414 0.3414 8-379

aaa

740 @ 1.40

ee

0.0010-0.0027 eet

Diesel

8-454

[email protected] | 15/4 | 0.0010-0.0027 | 0.0012-0.0029 | 0.3719

0.3719

® + 1/2 in. @ 172 @ 1.26 (1980)

@® Intake—123/s2 Exhaust— 119/32

@ Intake 44° Exhaust 30° © 1978-82: 46°

© 185@ 1.26 (1980) @ 1978-82: 121/32

Intake 45° Exhaust 31°

© 200 @ 1.16 exhaust 119/32 exhaust 85773c09

3-24

ENGINE AND ENGINE REBUILDING

CAMSHAFT

SPECIFICATIONS

(All measurements in inches)

Lobe Lift Engine

Year

Journal Diameter

Camshaft End Play

Exhaust

Intake

1980

ae

eT

1981

ES 1982-87

ee ae ee

Pe

a

|

.003-.008 .003-.008 .004-.012 .004-.012 .011-.077 .004-.012 .003-.008 .003-.008 .004-.012 .004-.012 .011-.077 .003-.008 .003-.008 .004-.012, .004-.012 .004-.012

, ® 1. 2, 3. 4.

2.0357-2.0365 2:0157-2.0165 1,9957-1.9965 1.9757-1.9765

Oapilegour=1- 9000 @ 2 #1,2,3,4: 2.1663-2: 1643 #5: 2.0088-2.0068 @ .2315 Calif. 85773d07

ENGINE AND ENGINE REBUILDING

3-25

CRANKSHAFT AND CONNECTING ROD SPECIFICATIONS All measurements are given in inches.

Year 1980-81

Engine No. Cyl. Displacement (cu. in.)

Main Brg. Journal Dia.

6-250

2.2979-2.2994

Crankshaft Main Brg. Oil Clearance

Connecting Rod Oil Clearance

Shaft End-play .002-.006

Thrust on No. 7

Journal Diameter 1.999-2.000

Nos. 1-6 .0010-.0024 No. 7 .0016-.0035

.002-.006

if

2.099-2.100

.0010-.0026

.006-.017

.0008-.0020}

.002-.006

5

2.199-2.200© | .0013-.0035

.008-.014

Nos. 1-6 .0010-.0024 No.7

Side = Clearance

.0010-.0026 | .006-.017

.0016-.0035

1982-87

6-292

2.2979-2.994

8-305, 350, 400

®

8-350 Diesel

2.9993-3.0003

Nos. 1-4 .0005-.0021 No.5 .0015-.0031

.0035-.0135)

5

2.1238-2.1248

6-250

2.2979-2.2994

Nos. 1-6 .0010-.0024 No.7 .0016-.0035

.002-.006

7

1.999-2.000

| 6262 | 6-292

8-305 350

oO

2.2979-2.994

® aoe

|

©

Nos. 1-6 .0010-.0024 No. 7 .0016-.0035

isaac ) Oheae 11 Oa

.013-.023 .005-.020

.0010-.0026

.006-.017

|.0020-.0060| 4 | 2.2487-2.2497_| 0020-0030 |.0070-.0150

-,0020@ -0008-.0020@|

©

| .0005-.0026

002-.006

7

.002-.006

002-007 | 5 | 20068.010).|

5.45

.0010-.0026

.006-.017

-2. 2.0988-2.0998 | .0013-.0035

008-.014

2.099-2.100

2.398-2.399

Bae

.007-.024

2.200-2.199 | .009-.0025

® No. 1: 2.7485-2.7494 Nos. 2-4: 2.7481-2.7490 No. 5: 2.7478-2.7488 ® Nos. 1-4: .0013-.0025 No. 5: .0024-.0040 @® 1977-1986: 305, 350 No. 1: 2.4484-2.4493 Nos. 2-4: 2.4481-2.4490 No. 5: 2.4479-2.4488 ® 1978-80: 2.0988-2.0998 © Nos. 1-4: 2.7481-2.7490 No. 5: 2.7476-2.7486

© Nos. 1-4: 2.9494-2.9504 No. 5: 2.9492-2.9502 ® Nos. 1-4: .0018-.0032 No. 5: .0022-.0037

Front: 2.4484-2.4493 Inter: Rear: © Front: Inter: Rear:

2.4481-2.4490 2.4479-2.4488 .0010-.0015 .0010-.0020 .0025-.0030

Nos. 2-4: .0011-.0023 No. 5: .0017-.0033 85773c08

ENGINE AND ENGINE REBUILDING

3-26

PISTON AND RING SPECIFICATIONS No.

Cylinder Displacement Year

VIN

ee

cu. in. (liter) 4.1 ae a

Piston

Top

Clearance

Compression

Ring Gap Bottom Compression

6-292 (4.8) ‘

8-305 (5.0)

Ring Side Clearance Bottom

Oil Control

Compression

Compression

Control

0.01500.0550 0.01500.0550

0.00120.0027 0.00200.0040

0.00120.0032

0.00050.0050

0.00200.0040

0.00050.0055

0.0150-

0.0012-

0.0012-

0.0020-

0.00120.0032 0.00170.0032 0.00120.0032 0.00200.0040 0.00120.0032 0.00120.0032 0.00120.0032

0.0070 0.00200.0070 0.00200.0070 0.00200.0070 0.00200.0070 0.00500.0065 0.00050.0050 0.00050.0085 0.00200.0070 0.00200.0070 0.00200.0070

8-305 (5.0) 8-350 (5.7) M

1981

8-350 (5.7) | 0.00070.0017

0.00070.0017 W | 8-454 (7.4) 0.00300.0040 6-250 (4.1) 0.00100.0020 6-292 (4.8) ih 0.00260.0036 F 8-305 (5.0) | 0.00070.0017 H 8-305 (5.0) | 0.00070.0017 Us 8-350 (5.7) | 0.00070.0017 8-350 (5.0) 0.0007P

8-350 (5.7)

0.0017

0.01000.0200 0.01000.0200 0.01000.0200

0.01300.0250 0.01000.0200 0.01000.0200

0.01500.0550 0.01500.0550 0.01500.0550

0.00120.0032 0.00170.0032 0.00120.0027

0.01000.0200 0.01000.0200

0.01000.0250 0.01300.0250

0.01500.0550 0.01500.0550

0.00120.0032 0.00120.0032

0.01000.0200

0.01300.0250 0.01300.0250 0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0250

| 0.01500.0550 | 0.01500.0550 | 0.01500.0550 | 0.01500.0550 | 0.01500.0550 | 0.01500.0550

8-350 (5.7 )

1982

6-250 (4.1) | 0.00100.0020 6-292 (4.8) | 0.00260.0036 8-305 (5.0) | 0.00070.0017 Se, 8-305 (5.0) | 0.00070.0017 8-350 (5.7) | 0.00070.0017 8-350 (5.7) | 0.0007| 0.0017 P | 8-350(5.7) | 0.00070.0017 C | 8-379 (6.2) ae 4

0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0200 0.01200.0220

0.01300.0250 0.01300.0250 0.03000.0400

, Oil

Top

| 0.00120.0032 | 0.00120.0032 | 0.00170.0032 | 0.00120.0027 | 0.00200.0040 | 0.00120.0032 0.00120.0032 0.00120.0032 | 0.0150- | 0.00120.0550 0.0032 | 0.0150- | 0.00120.0550 0.0032 | 0.0100- | 0.00300.0210 0.0071

0.0012- | 0.00200.0032 0.0070 0.0012- | 0.00200.0032 0.0070 0.0017- | 0.00500.0032 0.0065 0.0012- | 0.00050.0032 0.0050 0.0020- | 0.00050.0040 0.0055 0.0012- | 0.00200.0070 0.0032 0.0012- | 0.00200.0032 0.0070 0.0012- | 0.00200.0032 0.0070 0.0012- | 0.00200.0032 0.0070 0.0012- | 0.00200.0032 0.0070 0.0300- | 0.00160.0400 0.0038 8577310

ENGINE AND ENGINE REBUILDING

3-27

PISTON AND RING SPECIFICATIONS

Year

No. Cylinder Displacement _VIN__cu.in. (liter) J

1983

me

Piston Clearance

Top Compression

Ring Gap Bottom Compression

Oil Control

8-379 (6.2)

@

0.01200.0220

0.03000.0400

0.01000.0210

0.00300.0071

0.03000.0400

0.00160.0038

8-454 (7.4)

0.00300.0040

0.01000.0200

0.01000.0200

0.01500.0550

0.00170.0032

0.00170.0032

0.00500.0065

0.0010-

0.0100-

0.0100-

0.0150-

0.0012-

0.0012-

0.0005-

0.0020

0.0200

0.0200

0.0550

0.0027

0.0032

0.0050

6-250 (4.1)

6-292 (4.8) | 0.0026-

0.0100-

0.0100-

0.0200

0.0200

0.0100-

0.0100-

0.0017

0.0200

0.0250

0.0550

0.0032

0.0032

0.0070

0.00070.0017

0.01000.0200

0.01000.0250

0.01500.0550

0.00120.0032

0.00120.0032

0.00200.0070

L | 8-350(5.7) | 0.0007-

0.0100-

0.0130-

0.0012-

| 0.0020-

0.0200

0.0250

0.0036

8-305 (5.0) | 0.0007H

8-305 (5.0)

0.0017

8-350 (5.7)

0.01300.0250

8-350 (5.7)

0.01300.0250

| 0.0150- | 0.01200.0550

0.0027

| 0.0150- | 0.0012-

| 0.0150- | 0.00120.0550

0.0032

| 0.0150- | 0.00120.0550

0.0032

| 0.0150- | 0.0012-

0.0012-

0.0032

0.00120.0032

0.0012-

0.0032

0.0032

0.0030-

0.0300-

0.0071

0.0400

J | 8-379 (6.2)

0.0030-

0.0300-

D

8-454 (7.4) 6-250 (4.1)

bi

6-292 (4.8)

F

8-305 (5.0)

H

8-305 (5.0)

a

8-350 (5.7) 8-350 (5.7)

P

C

8-350 (5.7)

8-379 (6.2)

0.0550

0.00200.0040

C | 8-379 (6.2)

WwW 1984

Ring Side Clearance Top Bottom Oil ©Compression Compression _ Control

| 0.00050.0055

| 0.0020-

0.0070

| 0.00200.0070

| 0.00200.0070

| 0.00160.0038

| 0.0016-

0.0071

0.0400

0.0030-

0.0100-

0.0100-

0.0150-

0.0017-

0.0017-

0.0038 0.0050-

0.0040

0.0200

0.0200

0.0550

0.0032

0.0032

0.0065

0.0010-

0.0100-

0.0100-

0.0150-

0.0012-

0.0012-

0.0005-

0.0020 0.00260.0036 0.00070.0017 0.00070.0017 0.00070.0017 0.00070.0017 0.00070.0017

0.0200 0.01000.0200 0.01000.0200 0.01000.0200 0.01000.0200

0.0200 0.01000.0200 0.01000.0250 0.01000.0250 0.01300.0250

0.0550 0.01500.0550 0.01500.0550 0.01500.0550 0.01500.0550 0.01500.0550

0.0027 0.01200.0027 0.00120.0032 0.00120.0032 0.00120.0032 0.00120.0032

0.0032 0.00200.0040 0.00120.0032 0.00120.0032 0.00120.0032 0.00120.0032

0.0050 0.00050.0055 0.00200.0070 0.00200.0070 0.00200.0070 0.00200.0070

0.00300.0071

0.0032 0.03000.0400 0.03000.0400

0.00200.0070 0.00160.0038 0.00160.0038

| 0.0150- | 0.00170.0550 0.0032

0.00170.0032

| 0.00500.0065

®@

8-379 (6.2)

0.03000.0400

8-454 (7.4)

0.01000.0200

0.01000.0210

© Bohn Pistons 1-6—0.089-0.115mm 7-8—0.102-0.128mm Zollner Pistons 1-6—0.112-0.138mm

7-8—0.125-0.115mm 8577C10A

SeSe a,

ee a

ENGINE AND ENGINE REBUILDING

3-28

PISTON AND RING SPECIFICATIONS No. Cylinder

: Ring Gap_ Bottom

san xe Ring Side Clearance Bottom

Top Compression

Compression

' Oil Control

0.00120.0032

0.00200.0070

0.00200.0040

0.00050.0055

Year

VIN

Displacement cu. in. (liter)

Piston Clearance

Top Compression

Compression

Oil Control

1985

N

6-260 (4.3)

0.00070.0017

0.01000.0250

0.01000.0250

0.01500.0550

0.00120.0032

T

6-292 (4.8)

0.00260.0036

0.01000.0200

0.01000.0200

0.01500.0550

0.01200.0027

8-305 (5.0)

T0.00070.0017

0.01000.0200

0.01000.0250

0.01500.0550

0.00120.0032

8-305 (5.0)

0.00070.0017

0.01000.0200

0.00200.0070

8-350 (5.7)

0.00070.0017

0.01000.0200

0.00200.0070

M

8-350 (5.7)

0.00070.0017

0.01000.0200

0.01300.0250

0.01500.0550

0.00120.0032

0.00120.0032

0.00200.0070

C

8-379 (6.2)

@

0.01200.0220

0.0300-

0.01000.0210

0.00300.0071

0.03000.0400

0.00160.0038

0.01200.0220

0.03000.0400

0.01000.0210

0.00300.0071

0.03000.0400

0.00160.0038

L F as |

H L |

8-379 (6.2) +

1986

©

0.00200.0070

Ww

8-454 (7.4)

0.00300.0040

0.01000.0200

0.01000.0200

0.01500.0550

0.00170.0032

0.00170.0032

0.00500.0065

N

6-260 (4.3)

0.00070.0017

0.01000.0250

0.01000.0250

0.01500.0550

0.00120.0032

0.00120.0032

0.00200.0070

0.01000.0250

0.01000.0250

0.01500.0550

0.00120.0032

0.00120.0032

0.00200.0070

0.01000.0200

0.01000.0200

0.01500.0550

0.01200.0027

0.00200.0040

0.00050.0055

0.00120.0032

0.00200.0070

6-260 (4.3) 6-292 (4.8)

0.00260.0036 0.00070.0017 0.00070.0017

0.01000.0200

0.01000.0250

0.01500.0550

0.00120.0032

0.01000.0200

0.01000.0250

0.01500.0550

0.00120.0032

F

8-305 (5.0)

H

8-305 (5.0)

ILE

8-350 (5.7). | 0.0007vache 0.0017

0.01000.0200

0.01300.0250

0.01500.0550

0.00120.0032

M

§-350(6.7) $0.0007- | 0.01000.0017 0.0200

0.01300.0250

0.01500.0550

0.00120.0032

C

8-379 (6.2)

®

J

8-379 (6.2)

W

8-454 (7.4)

0.00200.0070 0.00200.0070

0.00120.0032

0.00200.0070

0.01200.0220

0.03000.0400

0.00160.0038

®

0.01200.0220

0.03000.0400

0.00160.0038

0.00300.0040

0.01000.0200

0.00170.0032

0.00500.0065 8577C10B

ENGINE AND ENGINE REBUILDING

3-29

PISTON AND RING SPECIFICATIONS

VIN

Year

1987

No. Cylinder Displacement cu. in. (liter)

Z | 6-260 (4.3)

Piston Clearance

Ring Gap Bottom Compression

Top Compression

0.01000.0250 T | 6-292 (4.8) 0.01000.0200 8-305 (5.0) | 0.0007- | 0.01000.0017 0.0200 8-350 (5.7) | 0.00070.0017 8-350 (5.7)

0.01000.0250 0.01000.0200 0.01000.0250

Oil Control

Ring Side Clearance Top Bottom Compression Compression

|

| 0.01500.0550 | 0.01500.0550 | 0.01500.0550 0.01500.0550 0.01500.0550

| 0.00120.0032 | 0.01200.0027 | 0.00120.0032 | 0.00120.0032 | 0.00120.0032

|

0.01500.0550

0.00120.0032

|

8-350 (5.7)

Oil Control

0.0012— 0.0032 0.00200.0040 0.00120.0032 0.00120.0032

8-379 (6.2) | 8-379 (6.2) | 8-454 (7.4) |

8-454 (7.4)

0.01000.0200 0.01000.0200

| 0.0150- | 0.00170.0550 0.0032 | 0.0150- | 0.00170.0550 0.0032

© Bohn Pistons 1-6—.089-. 115mm 7-8—.102-.128mm Zollner Pistons 1-6—.112-.138mm 7-8—.125-.115mm 8577C10C

t

ENGINE AND ENGINE REBUILDING

3-30

TORQUE SPECIFICATIONS (ft. Ibs.)

Engine . Cyl. rate unt

(cu. in.)

6-250

Rod: Bearing Bolts

Cylinder Head Bolts

Ol

a

; Main Bearing

Bolts

Crankshaft Bolt A

eo ee a

Flywheel to Crankshaft Bolts

600

950

6-292

8-305 8-350

a oe

8-350 Diesel

8-379 Diesel 8-396

© am||

—s

100®

8-400 8-454

-ne)

~So a er

—

nmcS

—

D>nrS S)

© oe No} o|S|®

© ow)w Ww) oO}0O!1m ©

=)

150@

Olala or 6nn

80

So © for) ~So

~)cSsa oo

Exhaust 300

aj

1

6-262

Manifold

Intake

rm] wic Ol1n

wo wo; =] S

a Pel

°rc)

—_ — —_ —

rep)a ©

o|— ww wo—)

rep) rep) i

no nmcos) ro)

A Front of crankshaft

© End bolts: 20 ft. Ibs.

® Dip in oil © Left-hand front bolt: 85 ft. Ibs. @® 1986-87: 50 ft. Ibs.

© 1986-87: outer bolts on #2, 3, 4 caps—70 ft. Ibs., all others 80 ft. Ibs. © 1986-87: 70 ft. Ibs. ® 1986-87: 75 ft. Ibs. 1986-87: 36 ft. Ibs.

© 1986-87: Cast manifolds: two center bolts—26 ft. Ibs. all others—20 ft. Ibs. Tubular (stainless steel): all bolts—26 ft. Ibs. 1986-87: 95 ft. Ibs. @ 1979-87: 85 ft. Ibs.

,

_® 1986-87: stainless steel man.—40 ft. Ibs.

:

cast iron man.—18 ft. Ibs. ® 1985-87: 1st 20 2nd 50

3rd 1/4 turn 1986-87: 200 ft. Ibs.

en

® 1986-87: 30 ft. Ibs.

fr

Center two bolts: 26 ft. Ibs. All others: 20 ft. Ibs.

® Inner: 110 Outer: 100 _ 85773c11

Engine CO REMOVAL & INSTALLATION The factory recommended procedure for engine removal is ‘to remove the engine/transmission as a unit on two wheel

drive models, except for the diesel. Only the engine should be

removed on diesels and four wheel drive models. 1. Disconnect the negative battery terminal. On diesels, dis-

connect the negative cables at the batteries and ground wires at the inner fender panel.

«CAUTION When draining the coolant, keep in mind that cats and ~ dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a

sealable container. Coolant should be reused unless it is

contaminated or several years old a)

3. Drain the engine oil.

.

4. Remove the air cleaner and ducts. 5. Scribe alignment marks around the hood hinges, and remove the hood. i

ENGINE AND ENGINE REBUILDING ES

ST

TST

EE

STS

6. Remove the radiator and hoses, and the fan shroud if so equipped. 7. Disconnect and label the wires at: . Starter solenoid. . Alternator. . Temperature switch. . Oil pressure switch. . Transmission controlled spark solenoid. . CEC solenoid. Coil. CO; 2Go AD. Neutral safety switche: TO 8. Disconnect: a...Accelerator linkage (hairpin at bellcrank, throttle and T.V. cables at intake manifold brackets on diesels.) Position away from the engine. b. Choke cable at carburetor, if so equipped. c. Release the fuel system pressure (see Section 1) and disconnect the fuel line to fuel pump. d. Heater hoses at engine. e. Air conditioning compressor with hoses attached. Do not remove the hoses from the air conditioning compressor. Remove it as a unit and set it aside. Its contents are under pressure, and can freeze body tissue on contact. e>R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, can contribute to the deple-

tion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun. If possible, an approved R-12 Recovery/Recycling machine that meets SAE standards should be employed when discharging the system. Follow the operating instructions provided with the equipment exactly to properly discharge the system. f. Transmission dipstick and tube on automatic transmission models, except for diesel. Plug the tube hole. g. Oil dipstick and tube. Plug the hole. h. Vacuum lines. i. Oil pressure line to gauge, if so equipped. j. Parking brake cable. k. Power steering pump. This can be removed as a unit and set aside, without removing any_of the hoses.

|. Engine ground straps. m. Exhaust pipe (suppert"if necessary). 9. Loosen and remo ¢ fan belt, remove the fan blades and pulley. If you have the finned aluminum viscous drive fan clutch, keep it upright in its normal position. If the fluid leaks out, the unit will have to be replaced. 10. Remove the clutch cross-shaft. 11. Attach a lifting device to the engine. You may have to remove the carburetor. Take the engine weight off the engine mounts, and unbolt the mounts. On all models except the gas engined and 4 ton, support and disconnect the transmission. With autOmatic transmission, remove the torque converter underpanjand starter, unbolt the converter from the flywheel, detach the throttle linkage and vacuum modulator line, and unbolt the engine from the transmission. Be certain that the converter does not fall out. With manual transmission, unbolt the clutch housing from the engine. Further details are in Section 7. 12. On two wheel drive models, remove the driveshaft. See details in Section 7. Either drain the transmission or plug the driveshaft opening. Disconnect the speedometer cable at the

SESS

SSS

STS

DS SERS

ST

TO

ES

ES

3-31 SOP

transmission. Disconnect the TCS switch wire, if so equipped. Disconnect the shift linkage or lever, or the clutch linkage.

Disconnect the transmission cooler lines, if so equipped. If you have an automatic or a four speed transmission, the rear

crossmember must be removed. With the three speed, unbolt the transmission from the crossmember. Raise the engine/transmission assembly and pull it forward. 13. On diesels, remove the three bolts, transmission, right

side; disconnect the wires to the starter and remove the Starter.

14. On four wheel drive, raise and pull the engine forward until it is free of the transmission. On diesels, slightly raise the transmission, remove the three left transmission to engine bolts, and remove the engine. 15. On all trucks, lift the engine out slowly, making certain as you go that all lines between the engine and the truck have been disconnected. To install: 16. On four wheel drive and diesels, lower the engine into place and align it with the transmission. Push the engine back gently and turn the crankshaft until the manual transmission shaft and clutch engage. Bolt the transmission to the engine. With automatic transmission, align the converter with the flywheel, bolt the transmission to the engine, bolt the converter to the flywheel, replace the underpan and starter, and connect the throttle linkage and vacuum modulator line. See Section 7 for details. 17. On two wheel drive, lower the engine/transmission unit

into place. Replace the rear crossmember if’removed. Bolt the three speed transmission back to the crossmember. Replace the driveshaft. 18. Install the engine mounts. 19. Replace all transmission connections and the clutch cross-shaft. Replace the fan, pulley, and belts. 20. Replace all the items removed from the engine earlier. — Connect all the wires which were detached.

21. Replace the radiator and fan shroud, air cleaner, and te battery or battery cables. Fill the cooling system and check the automatic transmission fuel level. Fill the crankcase with @ir®**~ Check for leaks. °

Valve Cover(s) REMOVAL & INSTALLATION » See Figures 42 and 43 1. Disconnect the negative battery cable. 2. Remove air cleaner. 3. Disconnect and reposition as necessary any vacuum or PCV hoses that obstruct the valve covers. 4. On the left side, on some models, it may be necessary to remove the air conditioning compressor and lay to one side. (Do not disconnect the hoses). ae = 5. Disconnect electrical wire(s), spark plug, etc. from the valve cover Clips. 6. Unbolt and remove the valve cover(s).

Do not pry the covers off if they seem stuck. Instead, gently tap around each cover with a rubber mallet until the old gasket or sealer breaks loose.

REBUILDING . “ENGINE AND ENGINE 3-32 e Cee e 4 )

To install: 7, Use a new valve cover gasket or RTV (or any equivalent) sealer. If using sealer, follow directions on the tube. Install valve cover and tighten cover bolts to 3 ft. Ibs. 8. Connect and reposition all vacuum and PCV hoses, and

reconnect electrical and/or spark plug wires at the cover clips. Install the air cleaner.

REMOVAL & INSTALLATION Gasoline Engines

» See Figures 44, 45 and 46 1. Remove the valve cover. 2. Remove the rocker arm nuts, then remove the rocker pivots. 3. Remove the rocker arms.

=>Remove each set of rocker arms (one set per cylinder) as a unit.

To install: 4. To install, position a set of rocker arms (for one cylinder) in the proper location. 28 FT. LBS. (38 N-m)

e>install the rocker arms for each cylinder only when the lifters are off the cam lobe and both valves are closed. ..

ROCKER ARM PIVOT ROCKER ARM FULLY DRIVEN SEATED. AND NOT STRIPPED

5. Coat the replacement rocker arm and pivot with SAE 90 gear oil and install the pivots. 6. Loosely install the rocker arm nuts, then properly adjust the valve lash. Please refer to the procedure later in this section.

85773029

Fig. 42 Valve cover and rocker removal arm removal,

common V8 engine shown — note that not all engines utilize bolt retained pivots

"85773166

Apply 2 3/32"' bead of R. TV. (room temperature vulcanizing) sealer on the valve cover

85773030

Fig. 43 Apply sealer to all valve covers as shown. Always run the sealer bead on the inside edge of the bolt holes on the cover flange

"85773167

Fig. 45 With the nut and pivot out of the way, the rocker arm may be removed

ENGINE AND ENGINE REBUILDING

3-33

sealed with a bead of RTV (Room Temperature Vulcanizing) silicone sealer. 8-379 (6.2L) Diesel

» See Figure 47 1. Disconnect the negative battery cable. 2. Remove the valve cover as previously explained. 3, The rocker assemblies on the 379 differ completely from those on the 350 diesel. The 379 arms are mounted on two short rocker shafts per cylinder head, with each shaft operating four rockers. Remove the two bolts which secure each rocker shaft assembly, and remove the shaft.

4. The rocker arms can be removed from the shaft by removing the cotter pin on the end of each shaft. The rocker arms and springs slide off. 5. To install, make sure first that the rocker arms and springs go back on the shafts in the exact order in which they were removed.

e> Always install new cotter pins on the rocker shaft ends. 6. Install the rocker shaft assemblies, torquing the bolts to 41 ft. Ibs. 85773031

ab

Valve Lash Adjustment » See Figures 48, 49, 50, 51 and 52

Fig. 46 Six-cylinder rocker arm components — all gasoline V8’s similar 8-350 Diesel

When the diesel engine rocker arms are removed or loosened, the lifters must be bled down to prevent oil pressure buildup inside each lifter, which could cause it to

raise up higher than normal and bring the valves within striking distance of the pistons. 1. Disconnect the negative battery cable. 2. Remove the valve cover. 3. Remove the rocker arm pivot bolts, the bridged pivot and rocker arms. 4. Remove each rocker set as a unit. 5. To install, lubricate the pivot wear point and position each set of rocker arms in its proper location. Do not tighten the pivot bolts for fear of bending the valves when the engine is turned. _ 6. The lifters can be bled down for 6 cylinders at once with the crankshaft in either of the following two positions: a. For cylinders number 3, 5, 7, 2, 4 and 8, turn the crankshaft so the saw slot on the harmonic balancer is at 0 degrees on the timing indicator.

>The valve lash adjustment procedure is for hydraulic lifters which are filled with oil either from previous use (old lifters on which the oil has not drained) or from priming before installation (new lifters or old lifters on which oil had drained while removed from the engine).

All engines described in this book use hydraulic lifters, which require no periodic adjustment. In the event of cylinder head removal or any operation that requires disturbing the rocker arms, the rocker arms will have to be adjusted. 1. Remove the rocker covers and gaskets. 2. Adjust the valves on in-line 6 cylinder engines as follows: a. Mark the distributor housing with a piece of chalk at the No. 1 and 6 plug wire positions. Remove the distributor cap with the plug wires attached. b. Crank the engine until the distributor rotor points to the NO. 1 cylinder and the No. 1 piston is at TDC (both No. 1

b. For cylinders 1, 3, 7, 2, 4 and 6, turn the crankshaft

so the saw slot on the harmonic balancer is a 4 o'clock. 7. Tighten the rocker arm pivot bolts VERY SLOWLY to 28 ft. Ibs. It will take 45 minutes to completely bleed down the lifters in this position. If additional lifters must be bled, rotate the engine to the other position, tighten the rocker arm pivot bolts, and again wait 45 minutes before rotating the crankshaft. Excess torque here can bend the pushrods, so be careful! 8. Assemble the remaining components in the reverse of disassemble. The rocker covers do not use gaskets, but are

OP NEY coe eu

85773032

Fig. 47 6.2L diesel rocker shaft assemblies

Baio

Mio? ast eG

ENGINE AND ENGINE REBUILDING

3-34

ffont |ELIEELIEEIIE 6 cylinder

ETE IIE ‘}

net atl at hae

FIVEEINE

Small block V8s

Qa

FRON

d. Crank the engine until the distributor rotor points to the No. 6 cylinder and the No. 6 piston is at TDC (both No. 6 cylinder valves closed). The following valves can be adjusted: e No. 2 Exhaust e No. 3 Intake e No. 4 Exhaust e No. 5 Intake e No. 6 Intake and Exhaust 3. Adjust the valves on V8 and V6 engines as follows: a. Crank the engine until the mark on the damper aligns with the TDC or 0 degree mark on the timing tab and the engine is in the No. 1 firing position. This can be determined by placing your fingers on the No. 1 cylinder valves as the marks align. If the valves do not move, it is in the No. 1 firing position. If the valves move, it is in the No. 6 firing position (No. 4 on V6) and the crankcase should be rotated one more revolution to the No. 1 firing position. b. With the engine in the No. 1 firing position, the following valves can be adjusted: e V8: Exhaust 1, 3, 4, 8

EbE PEs Ess Big block V8s 85773033

Fig. 48 Chevrolet Intake (I) and Exhaust (E) valve arrangements (except V6 engine)

e V8: Intake 1, 2, 5, 7 e V6: Exhaust 1, 5, 6 e V6: Intake 1, 2, 3 c. Back out the adjusting nut until lash is felt at the pushrod, then turn the adjusting nut in until all lash is removed. This can be determined by checking pushrod endplay while turning the adjusting nut. When all play has been removed, turn the adjusting nut in: e ‘'/-1', additional turn (flat lifter) @ %4-1'/4 additional turn (roller lifter V8) e %4 additional turn (roller lifter V6) d. Crank the engine 1 full revolution until the marks are again in alignment. This is the No. 6 firing position (No. 4 on V6). The following valves can now be adjusted: e V8: Exhaust 2, 5, 6, 7

e V8: Intake 3, 4, 6, 8 e V6: Exhaust 2, 3, 4 e V6: Intake 4, 5, 6

4. Reinstall the rocker arm covers using new gaskets or sealer. 85773034

5. Install the distributor cap and wire assembly. 6. Adjust the carburetor idle speed.

Fig. 49 V6 262 valve arrangement (E- Exhaust; I- Intake) |

cylinder valves closed). At this point, adjust the following

I i

valves: e © e e e

No. No. No. No. No.

1 2 3 4 5

Exhaust and Intake Intake Exhaust Intake Exhaust

c. Back out the adjusting nut until lash is felt at the pushrod, then turn the adjusting nut in until all lash is removed. This can be determined by checking pushrod endplay while turning the adjusting nut. When all play has been

removed, turn the adjusting nut in 1 full turn.

=

ae: ae

Fig. 50 Valve adjustment, all except 6.2L diesel

ENGINE AND ENGINE REBUILDING

3-35

been sealed with RTV sealant. If so, place a ‘/s inch bead of

RTV sealer all around the thermostat housing sealing surface on the intake manifold and install the housing while it is still wet. Refill the radiator to approximately 2‘ inch below the filler neck. elf the thermostat is equipped with a pin hole, be sure to install pin side facing upwards.

EXHAUST

Intake Manifold

VALVES

;

85773068

REMOVAL & INSTALLATION Fig. 51 Diesel 350 V8 valve location In-line 6-Cylinder PRE CHAMBER INTAKE

250 (4.1L) ENGINE

VALVES

All 250 (4.1L) engines have an intake manifold which is cast integrally with the cylinder head and cannot be removed.

PRE CHAMBER

292 (4.8L) ENGINE

EXHAUST

VALVES 85773069

Fig. 52 6.2L (379) diesel engine valve arrangement

Thermostat

:

;

REMOVAL & INSTALLATION 1. Drain the radiator until the coolant level is below the thermostat level (below the level of the intake manifold). . ¢

xk CAUTION

When draining the coolant, keep in mind that cats and

dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 2. Remove the water outlet elbow assembly from the engine. Remove the thermostat from inside the elbow. 3. Install new thermostat in the reverse order of removal, making sure the spring side is inserted into the elbow. Clean the gasket surfaces on the water outlet elbow and the intake manifold. Use a new gasket when installing the elbow to the manifold. On later models the thermostat housing may have

1. Disconnect the negative battery cable. 2. Remove the air cleaner assembly and air ducts. 3. Tag and disconnect the throttle linkage at the carburetor. Tag and disconnect the fuel line, vacuum lines, hoses, and electrical connections. 4. Disconnect the transmission downshift linkage (if equipped), and remove the PCV valve from the rocker cover. On models equipped with air injection, disconnect the air supply hose from the check valve on the air injection manifold. 5. Remove the carburetor, with spacer and heat shield (if equipped). 6. Spray the nuts and bolts connecting the exhaust manifold to the exhaust pipe with a rust penetrant, as these are usually quite difficult to remove. Unbolt the exhaust manifold from the pipe. =>It may be necessary to remove the generator rear bracket and/or air conditioning compressor bracket on some models. 7. Unbolt the manifold bolts and clamps, and remove the manifold assembly. 8. If you intend to separate the manifolds, remove the sin-

gle bolt and two nuts at the center of the manifold assembly. 9. Installation is the reverse of removal. When assembling the manifolds, install the connecting bolts loosely first. Place the manifolds on a straight, flat surface and hold them securely during tightening — this assures the proper mating of surfaces when the manifold assembly is fastened to the head. Stress cracking could occur if the manifolds are not assembled first in this manner. On all manifolds, always use new gaskets

between the manifold and cylinder head. V6 and V8 Except Diesel » See Figures 53, 54, 55, 56, 57, 58, 59 and 60

1. Disconnect the negative battery cable.

3-36

ENGINE AND ENGINE REBUILDING

2. Drain the cooling system.

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 85773170

3. Remove the air cleaner assembly. 4. Either remove the thermostat housing and the bypass hose, or if the manifold is not being replaced, you may just disconnect the hose. 5. Disconnect the heater hose at the rear of the manifold. 6. Disconnect all electrical connections and vacuum lines from the manifold. Remove the EGR valve if necessary. 7. On vehicles equipped with power brakes remove the vacuum line from the vacuum booster to the manifold. 8. Remove the distributor (if necessary). 9. Move the air conditioning compressor to one side, if necessary. 10. Relieve the fuel system pressure. See Section 1. 11. Remove the fuel line to the carburetor or TBI unit. 12. Remove the carburetor linkage.

Fig. 55 When all bolts are removed, the manifold may be lifted from the engine 13. Disengage the electrical connections at the TBI unit. 14. Remove the carburetor or TBI unit, if necessary. 15. Remove the intake manifold bolts. Remove the manifold and the gaskets. Remember to reinstall the O-ring seal between the intake manifold and timing chain cover during assembly, if so equipped. ->Most intake manifolds are cast iron and heavy. It will be necessary to get a good grip before attempting to lift the manifold from the engine. Also, the gasket seal may take some leverage to break, but be very careful not to damage the mating surfaces if prying is necessary. 16. Reconnect all wires, hoses and linkage. Use plastic gasket retainers to prevent the manifold gasket from slipping out of place, if so equipped. On the small block V8s, place a 4:6 inch bead of RTV type silicone sealer on the front and rear ridges of the cylinder block-to-manifold mating surfaces. Extend the bead ‘2 inch up each cylinder head to seal and retain the manifold side gaskets. ->Before installing the intake manifold, be sure that the gasket surfaces are thoroughly clean. 8-350 Diesel

73168

Fig. 53 Disengage all electrical connectors from the intake manifold mounted components

» See Figures 61, 62, 63, 64, 65, 66, 67 and 68

1. Disconnect the negative battery cable. 2. Remove the air cleaner.

85773169

85773035

Fig. 54 A box wrench will likely be needed on a few manifold bolts where manifold components restrict access

Fig. 56 305 and 350 V8 intake manifold bolt torque sequence

ENGINE AND ENGINE REBUILDING

INTAKE MANIFOLD BOLTS

47 Nm (35 Ft. Lbs.)

Grr

ODO

OG

p—tSerene

OD

3-37

oO

AH

WY

85773036

(INITIAL) INLET MANIFOLD BOLT/SCREW & STUDS TIGHTENING SEQUENCE

Fig. 57 396 and 454 intake manifold bolt torque sequence 3. Drain the radiator. Loosen the upper bypass hose clamp, remove the thermostat housing bolts, and remove the housing and the thermostat from the intake manifold.

22.9.9 (FINAL) INLET 29 BOLT/SCREW & STUDS TORQUE SEQUENCE

°K CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 4. Remove the breather pipes from the rocker covers and the air crossover. Remove the air crossover.

20 LB. FT. (27 Nem)

SWITCH

85773038

Fig. 59 V6 engine intake manifold torque sequence

CHOKE HOT AIR PIPE (2 CHOKE CLEAN AIR PIPE f

17 LB. FT. (23 Nem)

WATER OUTLET )

GASKET

40 LB. FT. (54 Nem)

“ENGINE LIFTING STRAP

BY-PASS HOSE

25LB. FT. (34 Nem)

THERMAL VACUUM SWITCH THERMOSTAT E.G.R. VALVE ADAPTER F. Sa

35 LB. FT. (48 Nem) 4

MANIFOLD rat GASKET

INTAKE MANIFOLD CROSS SECTION

E.G.R. PORTS (UNDER CARB. PRIMARY BORES)

PASSAGE 85773037

Fig. 58 Gasoline V8 engine intake manifold installation

| | i:

3-38

ENGINE AND ENGINE REBUILDING 16. Clean the intake manifold bolts thoroughly, then dip them in clean engine oil. Install the bolts and tighten to 15 ft. Ibs. in

the sequence shown. Next, tighten all the bolts to 30 ft. Ibs., in

sequence, and finally tighten to 40 ft. Ibs. in sequence. 17. Install the intake manifold drain tube and clamp. 18. Install injection pump adapter. See Section 5. If a new adapter is not being used, skip steps 4 and 9. 8-379 (6.2L) Diesel 1. Disconnect both batteries. 2. Remove the air cleaner assembly.

3. Remove the crankcase ventilator tubes, and disconnect

the secondary fuel filter lines. Remove the secondary filter and adaptor.

85773039

TRANS.TV OR DETENT CABLE BRACKET 40 FT. LBS. (54 Nem)

INTAKE MANIFOLD

Fig. 60 On small blocks, run a 3/16 in. bead of RTV sealer across the block and 1/2 in. up the sides of the block just prior to manifold installation 5. Disconnect the throttle rod and the return spring. If equipped with cruise control, remove the servo. 6. Remove the hairpin clip at the bellcrank and disconnect

the cables. Remove the throttle cable from the bracket on the manifold; position the cable away from the engine. Disconnect and label any wiring as necessary. 7. Remove the alternator bracket if necessary. If equipped with air conditioning, remove the compressor mounting bolts and move the compressor aside, without disconnecting any of the hoses. Remove the compressor mounting bracket from the intake manifold. 8. Disconnect the fuel line from the pump and the fuel filter. Remove the fuel filter and bracket. 9. Remove the fuel injection pump and lines. See Section 5, Fuel System, for procedures. 10. Disconnect and remove the vacuum pump or oil pump drive assembly from the rear of the engine. 11. Remove the intake manifold drain tube. 12. Remove the intake manifold bolts and remove the manifold.,Remove the adapter seal. Remove the injection pump adapter.

13. Clean the mating surfaces of the cylinder heads and the intake manifold using a putty knife. 14. Coat both sides of the gasket surface that seal the intake manifold to the cylinder heads with G.M. sealer No. 1050026 or equivalent. Position the intake manifold gaskets on the cylinder heads. Install the end seals, making sure that the ends are positioned under the cylinder heads. 15. Carefully lower the intake manifold into place on the engine.

FRONT &

bara at

pack, ¥, s

>

oe ae

THROTTLE CABLE BRACKET

TS heteptoene GASKET

85773040

Fig. 61 350 diesel intake manifold installation. Note sealer application

85773041

Fig. 62 350 V8 diesel intake manifold torque sequence

ENGINE AND ENGINE REBUILDING

3-39

TUB Noe DRAI

DRAIN TUBE CLAMP

85773045

Fig. 66 The index mark on the injection pump driven gear will be offset to the right when the No. 1 cylinder is at TDC

85773042

Fig. 63 350 diesel intake manifold drain tube

went

"0" RING

al LBS: (27 Nem)

(APPLY LUBE TO "O' RING BEFORE INSTALLING)

NOTICE: DO NOT OPERATE ENGINE WITHOUT VACUUM PUMP AS THIS IS THE DRIVE FOR THE ENGINE Oil PUMP AND ENGINE

LUBRICA

DAMAGE WOULD OCCUR

85773043 85773046

Fig. 64 Oil pump drive and vacuum pump, 350 diesel shown. 379 diesel pump similar SFT. LBS.

ADAPTER TO MANIFOLD SEAL

Fig. 67 Adapter seal installation with the special tool

25 ft Ibs.

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FUEL INJECTION PUMP ADAPTER

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85773044

85773047

Fig. 65 Adapter and seal details, 350 diesel

Fig. 68 Adapter timing mark application

4. Loosen the vacuum pump hold-down clamp and rotate the pump to gain access to the nearest manifold bolt. 5. Remove the EPR/EGR valve bracket, if equipped. 6. Remove the rear air conditioning bracket, if equipped. 7. Remove the intake manifold bolts; the infection line clips are retained by these bolts. 8. Remove the intake manifold. [wEWARNING

If the engine is to be further serviced with the manifold

: ; removed, install protective covers over the intake ports. |

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9. Clean the manifold gasket surfaces on the cylinder heads and install new gaskets before installing the manifold. =>The gaskets have an opening for the EGR valve on light duty installations; an insert covers this opening on heavy duty installations. 10. Install the manifold. Torque the bolts in the sequence illustrated. 11. The secondary filter must be filled with clean diesel fuel

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removal

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procedures to complete P

3-40 ENGINE AND ENGINE REBUILDING usually quite difficult to remove. Unbolt the exhaust manifold from the pipe.

Exhaust Manifold

=>It may be necessary to remove the generator rear bracket and/or air conditioning compressor bracket on some models. ‘

REMOVAL & INSTALLATION In-line 6-Cylinder

250 (4.1L) ENGINE » See Figure 69 1. Disconnect the negative battery cable. 2. Disconnect and remove the air cleaner assembly, including the carburetor preheat tube. 3. Remove power steering pump bracket and AIR pump brackets if equipped. 4. Remove PAIR pipes. 5. Disconnect the exhaust pipe at the exhaust manifold. You will probably have to use a liquid rust penetrant to free the bolts. 6. Remove the engine oil dipstick bracket bolt. 7. Liberally coat the manifold nuts with a rust penetrating lubricant. Remove the exhaust manifold bolts and remove the manifold. To install: 8. Mount the manifold on the cylinder head and start all bolts. 9. Torque the bolts to specification using the torque sequence illustrated. Complete the installation by reversing the removal procedure.

292 (4.8L) ENGINE 1. Disconnect the negative battery cable. 2. Remove the air cleaner assembly and air ducts. _, 8. Tag and disconnect the throttle linkage at the carburetor. Tag and disconnect the fuel line, vacuum lines, hoses, and electrical connections. 4. Disconnect the transmission downshift linkage (if equipped), and remove the PCV valve from the rocker cover. On models equipped with air injection, disconnect the air supply hose from the check valve on the air injection manifold. 5.» Remove the carburetor, with spacer and heat shield (if equipped). 6. Spray the nuts and bolts connecting the exhaust manifold to the exhaust pipe with a rust penetrant, as these are

7. Unbolt the manifold bolts and clamps, and remove the manifold assembly. ; 8. If you intend to separate the manifolds, remove the single bolt and two nuts at the center of the manifold assembly. To install: 9. Before reassembling the two manifolds, check the exhaust manifold for warpage by laying a straight edge across the full length of the exhaust ports. If at any point a gap of 0.030 inch (0.080 mm) or more exists, the manifold will not likely seat properly and will require replacement. 10. When reassembling the manifolds, install the connecting bolts loosely first. Place the manifolds on a straight, flat surface and hold them securely during tightening — this assures the proper mating of surfaces when the manifold assembly is fastened to the head. Stress cracking could occur if the manifolds are not assembled first in: this manner. 11. Position a manifold gasket over manifold end studs on the cylinder head. On all manifolds, always use new gaskets. 12. Align and install manifold assembly to the cylinder head. Initially tighten all bolts finger tight. 13. Torque all manifold to cylinder head bolts to 40 ft. Ibs.

(55 Nm). 14. Complete manifold attachment by torquing the inlet to exhaust manifold bolt and the two nuts at the center of the manifold to 45 ft. Ibs. (61 Nm). 15. Reconnect exhaust pipe to manifold using a new packing. 16. Install the carburetor, with spacer and heat shield (if equipped). 17. Reconnect the transmission downshift linkage, if equipped, and reinstall the PCV valve hose from the rocker cover. On models equipped with air injection, reconnect the air supply hose from the check valve on the air injection manifold. 18. Reconnect the throttle linkage at the carburetor. Reconnect the fuel line, vacuum lines, hoses, and electrical connections. 19. Reinstall the air cleaner assembly and air ducts. 20. Reconnect. negative battery cable. Gasoline V6 and V8s

» See Figures 70, 71, 72, 73, 74, 75 and 76

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Tab locks are used on the front and rear pairs of bolts on each exhaust manifold. When removing the bolts, straighten the tabs from beneath the car using a suitable tool. When

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installing the tab locks, bend the tabs against the sides of the

35-40 ft.lbs.

40-45 ft. Ibs.

TIGHTENING SEQUENCE 85773048

Fig. 69 250 (4.1L) in-line six exhaust manifold torque sequence

bolts, not over the top of the bolt. 1. Disconnect the negative battery cable. 2. Remove the air cleaner. 3. Remove the hot air shroud, if equipped. 4. Loosen the alternator and remove its lower bracket. 5. Raise the truck and support itsafely using jackstands. It will be easiest for the following steps if the truck is supported _at a height which will allow for both underhood and undervehicle access.

ENGINE AND ENGINE REBUILDING ES

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6. Disconnect remove the stud moving the pipe 7. Lower the

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the crossover pipe from both manifolds by nuts, carefully lowering the pipe and by recollars (if equipped). vehicle, as necessary, for underhood access.

e>On models with air conditioning it may be necessary to remove the compressor, and tie it out of the way. Do not disconnect the compressor lines. 8. Remove the manifold bolts and remove the manifold(s). Some models have lock tabs on the front and rear manifold bolts which must be removed before removing the bolts. These tabs can be bent with a drift pin. 9. Reverse the above to install. Torque the bolts to specifications and bend the tab washers over the heads of all bolts.

8577317

Fig. 72 To loosen the exhaust manifold mounting nuts you will need a deep socket or a box wrench

8-350 Diesel V8 LEFT SIDE 1. Remove the air cleaner and cover the air crossover with a protective plate, screen or cover. Remove the lower generator bracket. Jack up the truck and safely support it with jackstands. Remove the exhaust pipe at the manifold flange. Lower the truck. Remove the exhaust manifold from above. NOORwWN . Reverse the above procedure to install. Torque the manifold nuts and bolts according to the illustration.

85773175

Fig. 73 Once the nuts are removed, carefully pull the manifold back and free from the studs

RIGHT SIDE 1. Jack up the truck and safely support it with jackstands. 2. Disconnect the exhaust pipe at the manifold flange.

85773171

Fig. 70 Be careful when removing the crossover pipe stud nuts, some applications are spring loaded and may jump loose while unthreading

Fig. 74 Here the exhaust manifold has just been removed along with 2 of its 3 gaskets

3. Remove the manifold. 4. Reverse the above procedure to install, torquing the manifold bolts according to the accompanying illustration. 8-379 Diesel V8

» See Figure 77 RIGHT SIDE

85773173

Fig. 71 Some applications use a collar to achieve a better seal between the crossover pipe and the exhaust

manifold

1. Disconnect the batteries. 2. Jack up the truck and safely support it with jackstands. 3. Disconnect the exhaust pipe from the manifold flange and lower the truck. 4. Disconnect the glow plug wires. 5. Remove the air cleaner duct bracket. 6. Remove the glow plug wires.

AS

3-42

ENGINE AND ENGINE REBUILDING 7. Reverse the above procedure to install. Start the manifold bolts while the truck is jacked up first. Torque the bolts to 25 ft. Ibs.

All pick-up trucks are equipped with cross-flow type radiators.

PLASTIC GASKET RETAINERS

REMOVAL & INSTALLATION 85773049

» See Figures 78, 79, 80, 81, 82, 83 and 84

Fig. 75 Plastic manifold gasket retainers, gasoline V8’s

1. Drain the radiator by opening the drain cock.

2 CAUTION When draining the coolant, keep in mind that cats and

dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

2. Disconnect the hoses and automatic transmission cooler line, if equipped. Plug the cooler lines to prevent system contamination or excessive fluid loss. Diesels should be equipped with both transmission cooler and oil cooler lines. 3. Disconnect the coolant recovery system hose. 4. If the vehicle is equipped with a fan shroud, detach the shroud and hang it over the fan to provide clearance. If equipped with a 2-piece shroud, the upper half may be re-

(EXC. CALIF.) UPPER SHROUD (CALIF. ) 85773050

moved for additional access. 5. On 6 cylinder engines, remove the finger guard. 6. Remove the mounting panel from the radiator support and remove the upper mounting pads. 7. Lift the radiator up and out of the truck. Lift the shroud out if necessary. 8. Reverse the above to install. Fill the cooling system and check the automatic transmission fluid level, and run the engine, checking for leaks.

Fig. 76 Gasoline V8 exhaust manifold with hot air

shrouds

sa

Engine Fan and Clutch

7. Remove the manifold bolts and remove the manifold. 8. To install, reverse the above procedure and torque the bolts to 25 ft. Ibs.

REMOVAL & INSTALLATION

LEFT SIDE

» See Figures 85 and 86

1.-Disconnect the batteries. 2. Remove the dipstick tube nut, and remove the dipstick tube. 3. Disconnect the glow plug wires. 4. Jack up the truck and safely support it with jackstands. &. Disconnect the exhaust pipe at the manifold flange.

1. Disconnect the negative battery cable 2. If necessary for access, remove radiator fan shroud. 3. Remove fan hub-to-water pump attaching bolts and remove fan clutch assembly. If vehicle is equipped with a fan clutch be sure to scribe a mark on both the fan and water pump to ease reassembly. 4. If necessary, femove the fan from the fan clutch hub. -To install : 5. Clean the water pump hub and check for smoothness. . Eliminate burrs or imperfections before proceeding. '

6. Remove the manifold bolts. Remove the manifold from underneath the truck. :

sass

ENGINE AND ENGINE REBUILDING

3-43

40 N-m

A

(30 FT. LBS.)

85773052

85773176

Fig. 78 If equipped, disconnect the automatic transmission cooler lines from the radiator using a line wrench

85773178

Fig. 80 Remove the bolts attaching the radiator shroud to the radiator

85773179

‘ h Fig. 81 If the vehicle is equipped with a 2-piece shroud, Fig. 79 Disconnect the coolant recovery tank hose from:|, , | the upper half-may be removed by loosening the the radiator ) | retainers

.

3-44. ee

ENGINE AND ENGINE REBUILDING

pS

"85773180

:

Fig. 82 Remove the radiator upper mounting panel retainers in order to remove the radiator

85773181 85773055

Fig. 85 Use an open-end or box wrench to loosen the nuts retaining the fan and clutch assembly

Fig. 84 Coolant recovery tank 6. Install fan cutch hub to water pump. Torque attaching

bolts to 20 Ib. ft. (27 Nm) CAUTION

Auxiliary Cooling Fan

If a fan blade is bent or damaged, no attempt should be made to repair the damaged fan. A damaged fan should always be replaced with a new assembly. It is important that the fan remains in proper balance. If a fan were not in balance it could possibly fly apart and result in personal ae

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1. Disconnect ‘the negative battery cable. 2. Remove the grille assembly. 3. Disconnect the harness connector from the auxiliary fan.

4. Remove the four attaching bolts from the radiator support.

7. lf removed, install the fan shroud.

5. To install, follow the procedure in the reverse order.

8. Reconnect the negative battery cable.

CK 200-300 5.7 AUTO-ALL CK-100 5.0-5.7 AUTO W/A/C OR H.D. COOLING 6.6-7.4-ALL : 5.7-DIESEL-ALL

REMOVAL & INSTALLATION

Air We 5.0-5.7-MAN.-ALL CK-100 5.0-5.7-AUTO W/O A/C OR H.D. COOLING 4.1-4.8-ALL W/A/C

4,1-4.8-ALL W/O A/C 85773053

Fig. 83 Radiator mounting

ENGINE AND ENGINE REBUILDING

3-45

a

Fig. 87 Once the fan clutch has been removed, the pulley may be pulled from the water pump hub engines, remove the water pump straight out of the block to avoid damaging the impeller.

Do not store viscous drive (thermostatic) fan clutches in any other position than the normal installed position. They should be supported so that the clutch disc remains vertical; otherwise, silicone fluid may leak out.

85773183

Fig. 86 With the fan shroud positioned aside, lift the clutch fan upward and from the vehicle

Water Pump

6. Check the water pump shaft bearings for end-play or roughness in operation. Water pump bearings usually emit a squealing sound with the engine running when the bearings need to be replaced. Replace the pump with a rebuilt or new pump (usually on an exchange basis) if the bearings are not in good shape or have been noisy.

|

REMOVAL & INSTALLATION All Except 379 (6.2L) Diesel

» See Figures 87, 88, 89 and 90 1. Disconnect the negative battery cable. 2. Drain the radiator and loosen the fan pulley bolts. 85773185

CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. a

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Fig. 88 Access to some water pump bolts will require various length extensions

LIE TE ELIE TI

3. Disconnect the heater and radiator hoses from the water pump assembly. 4. Loosen the alternator swivel bolt and remove the fan belt. Remove the fan bolts, fan and pulley. 5. Remove the water pump attaching bolts, noting the bolt positions for proper installation. Once the bolts are removed, separate the pump and gaskets from the engine. On in-line

85773186

Fig. 89 Other water pump bolts may be removed using only the ratchet and a socket

3-46

ENGINE AND ENGINE REBUILDING 14. Assemble the remaining components in the reverse order of removal. Fill the cooling system, start the engine and check for leaks.

Cylinder Head REMOVAL & INSTALLATION EY

85773187

Fig. 90 Once the bolts are removed, the water pump may be separated from the engine block 7. Installation is the reverse of removal. Clean the gasket surfaces and install new gaskets. Coat the gasket with sealer. On fans which mount using bolts instead of nuts, a ‘6 inch-24 x 1 inch guide stud installed in one hole of the fan will make installing the fan onto the hub easier. It can be removed after the other 3 bolts are started. Fill the cooling system and adjust the fan belt tension. Torque the pump retaining bolts to 15 ft.

Ibs. 8-379 Diesel 1. Disconnect the batteries. 2. Remove the fan and fan shroud. 3. Drain the radiator.

CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 4. If the truck is equipped with air conditioning, remove the air conditioning hose bracket nuts. 5. Remove the oil fill tube. 6. Remove the generator pivot bolt and remove the generator belt. 7. Remove the generator lower bracket. 8. Remove the power steering belt. Remove the power Steering belt and secure it out of the way. 9. Remove the air conditioning belt if equipped. 10. Disconnect the by-pass hose and the lower radiator hose. 11. Remove the water pump bolts. Remove the water pump plate and gasket and water pump. If the pump gasket is to be replaced, remove the plate attaching bolts to the water pump and remove (and replace) the gasket. 12. When installing the pump, the flanges must be free of oil. Apply an anaerobic sealer (GM part No. 1052357 or equivalent) as shown in the accompanying illustration. >The sealer must be wet to the touch when the bolts are

torqued. 13. Attach the water pump and plate assembly. Torque the plate bolts to 18 ft. lbs. and the pump bolts to 35 ft. Ibs.

In-line 6-Cylinder » See Figure 91

4

1. Disconnect the negative battery cable. 2. Drain the cooling system and remove the air cleaner assembly. Disconnect the PCV hose.

«CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 3. Tag and disconnect the throttle linkage at the carburetor. Tag and disconnect the fuel line, vacuum lines, and any electrical connections at the carburetor. 4. Remove the top radiator hose, and the battery ground strap. Disconnect the wires from the temperature sending unit, leaving the harness clear of the clips on the rocker cover. 5. Disconnect the coil wires after tagging them, and remove the coil. Tag and disconnect the spark plug wires from the plugs.

6. Remove the intake and exhaust manifolds. = On the 250 (4.1L) engine, the intake manifold is an integral part of the cylinder head. 7. Remove the rocker arm cover. Back off the rocker arm nuts, and pivot the rocker arms so the pushrods will clear. 8. Take a piece of heavy cardboard and cut 12 holes in it the same diameter as the pushrod stem. Number the holes in relation to the pushrods being removed. This cardboard holder will keep the pushrods in order (and hopefully out of harms way) while they are out of the engine. Remove the pushrods one at a time.

e*Pushrods MUST be returned to their original locations. 9. Remove the cylinder head bolts one at a time, and mark

them or keep them in order, as they should go back in their original locations. You may need a flex bar on your socket, or a piece of pipe on your ratchet, as the bolts are under a lot of torque.

10. Remove the cylinder head, along with the gasket. If the head seems stuck to the block, gently tap around the edge of the head with a rubber mallet until the joint breaks. NEVER pry between the head and block as you may gouge one or the other. Often it is necessary to carefully scrape the top of the engine block and the cylinder head to completely remove the gasket.

ENGINE AND ENGINE REBUILDING SR

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YEAR

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11. Clean the bottom of the head and top of block thoroughly before reinstalling the head. Place a new gasket over the dowel pin in the top of the block. =Different types of head gaskets are available. If you are using a steel/asbestos composition gasket, do not use gasket sealer. 12. Lower the cylinder head carefully onto the block, over the dowel pins and gasket. 13. Coat the heads and threads of the cylinder head bolts with sealing compound, GM part No. 1052080 or equivalent, and install finger tight. 14. Tighten the heads bolts gradually in three stages, following the sequence illustrated, to the specification listed under Torque Specifications. 15. Install the pushrods in the exact location from which they were removed. Make sure they are seated in their lifter sockets. 16. Swing the rocker arms over into the correct position. Tighten the rocker arms until all pushrod play is taken up. 17. Install the manifold assembly, using new gaskets. Torque the manifold(s) to the specified torque. 18. Reverse the remainder of the removal procedure for installation. Adjust the valves, following the procedure in this Section. Use a new gasket or high temperature sealer when installing the rocker arm cover. Gasoline V6 and V8s

» See Figures 92, 93, 94, 95, 96, 97, 98 and 99

1. Disconnect the negative battery cable.

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3-47 BSED

ESSIEN

2. Drain the coolant and save it if still fresh.

+ CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 3. Remove the air cleaner. 4. Remove the air conditioning compressor, but do not disconnect any air conditioning lines. Secure the compressor to one side. 5. Disconnect the AIR hose .at the check valve. 6. Remove the intake manifold. 7. When removing the right cylinder head, loosen the alter- nator belt, disconnect the wiring and remove the alternator. 8. When removing the left cylinder head, remove the dipstick, power steering pump and air pump if so equipped. 9. Label the spark plug wires and disconnect them. 10. Disconnect the exhaust manifold from the head being removed and reposition the manifold aside. 11. Remove the valve cover. Scribe the rocker arms with an identifying mark for reassembly; it is important that the rocker assembly is reinstalled in the same position as it was removed. Remove the rocker arm nuts, rocker arms and pivots. 12. Take a piece of heavy cardboard and cut 12 (V6), 16 holes (V8) (or half the number of holes if you are- only remov-

85773056

85773188

Fig. 91 250 and 292 six cylinder head bolt torque sequence

Fig. 92 When removing either of the cylinder heads, you must first remove the intake manifold assembly

3-48

ENGINE AND ENGINE REBUILDING

Fig. 96 Remove the old gasket from the engine block and discard

85773057

85773190

Fig. 93 Disconnect and reposition the exhaust manifold from the cylinder head that is being removed

Fig. 97 Small-block V8 cylinder head torque sequence

85773058

85773189

Fig. 94 Loosen the retainers and remove the valve covers from the cylinder head(s) being removed

Fig. 98 Big-block V8 torque sequence ing one head) in it the same diameter as the pushrod stem. Number the holes in relation to the pushrods being removed. This cardboard holder will keep the pushrods in order (and hopefully out of harm’s way) while they are out of the engine. Remove the pushrods.

e>Pushrods MUST be returned to their original locations. 13. On models equipped with power brakes, it may be necessary to disconnect the brake booster and turn it sideways to remove the No.7 pushrod. —

Fig. 95 Loosen and remove the cylinder head bolts using a large ratchet or breaker bar and suitably sized socket

14. Check to make sure all wires are disconnected from the

cylinder head. 15. Remove the cylinder head bolts, and remove the cylinder head and gasket. If the head seems stuck to the block, gently

ENGINE AND ENGINE REBUILDING SAAN

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SS

tap around the edge of the head with a rubber mallet until the joint breaks. To install: 16. Position a new cylinder head gasket, then install the cylinder head to the engine block. 17. Coat the threads of the cylinder head bolts with sealing compound, GM part No. 1052080 or equivalent, and install finger-tight. 18. Tighten the bolts to specification using the proper torque sequence. For proper torque specification, refer to the chart located earlier in this section. e*When installing the intake manifold remember to use new gaskets. 19. Reverse the removal procedure to complete installation. Be sure to install the rocker arms and push rods in their original positions. Adjust the valves as outlined earlier. Diesel Engines

» See Figure 100 1. Disconnect the negative battery cable. 2. Remove the intake manifold, using the procedure outlined above. 3. Remove the rocker arm cover(s), after removing any accessory brackets which interfere with cover removal. 4. Disconnect and label the glow plug wiring. 5. If the right cylinder head is being removed, remove the ground strap from the head. 6. On the 350, remove the rocker arms bolts, the bridged pivots, the rocker arms, and the pushrods, keeping all the parts in order so that they can be returned to their original positions. On the 379, remove the rocker shaft assemblies. It is a good practice to number or mark the parts to avoid interchanging them. 7. Remove the fuel return lines from the nozzles. 8. Remove the exhaust manifold(s), using the procedure outlined earlier in this Section. 9. On the 8-350, remove the engine block drain plug on the side of the engine from which the cylinder head is being removed. 10. Remove the head bolts. Remove the cylinder head. 11. To install, first clean the mating surfaces thoroughly. Install new head gaskets on the engine block. DO NOT coat the gaskets with any sealer on the either engine. The gaskets have a special coating that eliminates the need for sealer. The

000008 85773060

Fig. 99 V6 262 cylinder head torque sequence

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TSS WSS

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BSN

RT

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NDP

3-49 ATS

use of sealer will interfere with this coating and cause leaks. Install the cylinder head onto the block. 12. Clean the head bolts thoroughly. On the 350, dip the bolts in clean engine oil and install them into the cylinder block until the heads of the bolts lightly contact the cylinder head. On the 379, the left rear head bolt must be installed into the head prior to head installation. Coat the threads of the 379 cylinder head bolts with sealing compound (GM part No. 1052080 or equivalent) before installation. 13. On the 350, tighten the bolts in the illustrated sequence to 100 ft. lbs. When all the bolts have been tightened to this figure, begin the tightening sequence again, and torque all bolts to 130 ft. lbs. On the 379, tighten each bolt gradually in the sequence shown until the final torque specified (100 ft. lbs.) is met. 14. Install the engine block drain plugs on the 350, the exhaust manifolds, the fuel return lines, the glow plug wiring, and the ground strap for the right cylinder head. 15. Install the valve train assembly. Refer to the Diesel Engine Rocker Arm Replacement in this Section for the valve lifter bleeding procedures. 16. Install the intake manifold. 17. Install the valve covers. These are sealed with RTV-type silicone sealer instead of a gasket. See the Valve Cover procedure for proper sealer application. Install the cover to the head within 10 minutes, while the sealer is still wet.

CLEANING AND INSPECTION » See Figure 101 me»Any diesel cylinder head work should be handled by a reputable machine shop familiar with diesel engines. Disassembly, valve lapping, and assembly can be completed by following the gasoline engine procedures. Once the complete valve train has been removed from the cylinder head(s), the head itself can be inspected, cleaned and machined (if necessary). Set the head(s) on a clean work space, so the combustion chambers are facing up. Begin cleaning the chambers and ports with a hardwood chisel or other non-metallic tool.(to avoid nicking or gouging the chamber, ports, and especially the valve seats). Chip away the major carbon deposits, then remove the remainder of carbon with a wire brush fitted to an electric drill. Be sure that the carbon is actually removed, rather than just burnished. After decarbonizing is completed, take the head(s)

ae 85773061

Fig. 100 379 diesel cylinder head torque sequence

3-50

ENGINE AND ENGINE REBUILDING

to a machine shop and have the head hot tanked. In this process, the head is lowered into a hot chemical bath that very effectively cleans all grease, corrosion, and scale from all internal and external head surfaces. Also have the machinist check the valve seats and recut them if necessary. When you bring the clean head(s) home, place them on a clean surface. Completely clean the entire valve train with solvent.

1 & 3 CHECK DIAGONALLY 2 CHECK ACROSS CENTER

——

RESURFACING 85773063

» See Figures 102 and 103 Lay the head down with the combustion chambers facing up. Place a straightedge across the gasket surface of the head, both diagonally and straight across the center. Using a flat feeler gauge, determine the clearance at the center of the straightedge. If warpage exceeds 0.003 inch in a 6 inch span, or 0.006 inch over the total length, the cylinder head must be resurfaced. Resurfacing can be performed at most machine shops.

s>When resurfacing the cylinder head(s) of V8 engines, the intake manifold mounting position is altered, and must

~

be corrected by machining a proportionate amount from the intake manifold flange.

WIRE

BRUSH

Fig. 103 Be sure to check the head across the center and both diagonals of the mating surface

Valves & Springs REMOVAL » See Figures 104, 105, 106, 107, 108 and 109

Cylinder Heads Removed 1. Remove the head(s), and place on a clean surface. 2. Using a suitable spring compressor (for pushrod type overhead valve engines), compress the valve spring and remove the valve spring cap key. Release the spring compressor and remove the valve spring and cap (and valve rotator on some engines).

e>Use care in removing the keys; they are easily lost.

85773062

Fig. 101 Use a wire brush and electric drill to remove carbon from the combustion chamber and exhaust ports

3. Remove the valve seals from the intake valve guides. Throw these old seals away, as you'll be installing new seals during reassembly. 4. Slide the valves out of the head from the combustion chamber side. 5. Make a holder for the valves out of a piece of wood or cardboard, as outlined for the pushrods in gasoline engine Cylinder Head Removal. Make sure you number each hole in the cardboard to keep the valves in proper order. Slide the valves out of the head from the combustion chamber side; they MUST be installed as they were removed.

VALVE SPRING COMPRESSOR

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6

Fig. 102 Check the cylinder head mating surface for warpage using a precision straight edge and a feeler gauge

x7

2!

Ce ( 85773064

Fig. 104 Compressing the valve springs using a leverage-type valve spring compressor

ENGINE AND ENGINE REBUILDING

3-51

3. Install the air line adapter (GM tool No. J-23590 or equivalent) into the spark plug hole. Turn on the air compressor to apply compressed air into the cylinder. This keeps the valves up in place. e>Set the regulator of the air compressor at least 50 pounds to ensure adequate pressure. 4. Using the valve spring compressor, compress the valve spring and remove the valve keys and keepers, the valve spring and damper. 5. Remove the valve stem seal. 6. To reassemble, oil the valve stem and new seal. Install a new seal over the valve stem. Set the spring, damper and keeper in place. Compress the spring. Coat the keys with grease to hold them onto the valve stem and install the keys, making sure they are seated fully in the keeper grooves. Reinstall the valve cover after adjusting the valves, as outlined in this Section.

85773197

Fig. 105 With the valve spring compressed (using a jawed-type compressor here), the valve key is being removed using a magnet

INSPECTION » See Figure 110

Fig. 106 With valve spring compression released, the valve stem cap or upper spring seat retainer may be removed

Inspect the valve faces and seats (in the head) for pits, burned spots and other evidence of poor seating. If a valve face is in such bad shape that the head of the valve must be. ground in order to true up the face, discard the valve because the sharp edge will run too hot. The correct angle for valve faces is 45 degrees. We recommend the refacing be done at a reputable machine shop.

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85773199

Fig. 107 Remove the upper spring set for access to the valve spring

85773200

Fig. 108 Remove the valve spring from the stem and cylinder head

Cylinder Head(s) Installed It is often not necessary to remove the cylinder head(s) in order to service the valve train. Such is the case when valve seals need to be replaced. Valve seals can be easily replaced with the head(s) on the engine; the only special equipment needed for this job are an air line adapter (sold in most auto parts stores), which screws a compressed air line into the spark plug hole of the cylinder on which you are working, and a valve spring compressor. A source of compressed air is needed, of course. 1. Remove the valve cover. 2. Remove the spark plug, rocker arm and push rod on the

cylinder(s) to be serviced.

85773201

Fig. 109 The upper O-ring seal may be removed by hand

3-52 hd

REBUILDING ENGINE a ENGINE AND aA ashlee

Check the valve stem for scoring and burned spots. If not noticeably scored or damaged, clean the valve stem with solvent to remove all gum and varnish. Clean the valve guides using solvent and an expanding wire type valve guide cleaner. If you have access to a dial indicator for measuring valve stem-to-guide clearance, mount it so that the stem of the indicator is at 90 degrees to the valve stem, and as close to the valve guide as possible. Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator. Measure the valve stems using a micrometer, and compare to specifications to determine whether stem or guide wear is responsible for the excess clearance. If a dial indicator and micrometer are not available to you, take your cylinder head and valves to a reputable machine shop for inspection. Some of the engines covered in this guide are equipped with valve rotators, which double as valve spring caps. In normal operation the rotators put a certain degree of wear on the tip of the valve stem; this wear appears as concentric rings on the stem tip. However, if the rotator is not working properly, the wear may appear as straight notches or X patterns across the valve stem tip. Whenever the valves are removed from the cylinder head, the tips should be inspected for improper pattern, which could indicate valve rotator problems. Valve stem tips will have to be ground flat if rotator patterns are severe.

5. Remove the valve and tool, and remove ALL traces of

grinding compound with solvent soaked rag, or rinse the head with solvent.

e»Valve lapping can also be done by fastening a suction cup to a piece of drill rod in a hand egg beater type drill. Proceed as above, using the drill as a lapping tool. Due to the higher speeds involved when using the hand drill, care must be exercised to avoid grooving the seat. Lift the tool and change direction of rotation often.

SPRING HEIGHT AND PRESSURE CHECK » See Figure 112

LAPPING THE VALVES

1. Place the valve spring on a flat, clean surface next to a square. 2. Measure the height of the spring, and rotate it against the edge of the square to measure distortion (out-of-roundness). If spring height varies between springs by more than ‘16 inch or if the distortion exceeds ‘/16 inch replace the spring. A valve spring tester is needed to test spring test pressure, so the valve springs must usually be taken to a professional machine shop for this test. Spring pressure at the installed and compressed heights is checked, and a tolerance of plus or minus 5 Ibs. is permissible on the springs covered in this guide.

» See Figure 111

VALVE INSTALLATION

When valve faces and seats have been refaced and recut, or if they are determined to be in good condition, the valves must be lapped in to ensure efficient sealing when the valve closes against the seat. 1. Invert the cylinder head so that the combustion chambers are facing up. 2. Lightly lubricate the valve stems with clean oil, and coat the valve seats with valve grinding compound. Install the valves in the head as numbered. 3. Attach the suction cup of a valve lapping tool to a valve head. You'll probably have to moisten the cup to securely attach the tool to the valve. 4. Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving. Lap the valve until a smooth, polished seat is evident (you may have to add a bit more compound after some lapping is done).

» See Figure 113 e*For installing new valve stem seals without removing the cylinder head(s), see the procedure under Valves and Springs — Cylinder Head(s) Installed earlier in this Section.

New valve seals must be installed when the valve train is put back together. Certain seals slip over the valve stem and

guide boss, while others require that the boss be machined. In some applications Teflon® guide seals are available. Check with a machinist and/or automotive parts store for a suggestion on the proper seals to use. e*Remember that when installing valve seals, a small

amount of oil must be able to pass the seal to lubricate the valve guides; otherwise, excessive wear will result.

1. Lubricate the valve stems with clean engine oil.

85773202

Fig. 110 Measuring the valve stem-to-guide clearance using a dial indicator

Fig. 111 Lapping the valves by hand

ENGINE AND ENGINE REBUILDING

3-53

Valve Guides.

85773066

Fig. 112 Check valve spring installed height

RETAINER

The engines covered in this guide use integral valve guides; that is, they are a part of the cylinder head and cannot be replaced. The guides can, however, be reamed oversize if they are found to be worn past an acceptable limit. Occasionally, a valve guide bore will be oversize as manufactured. These are marked on the inboard side of the cylinder heads on the machined surface just above the intake manifold. If the guides must be reamed (this service is available at most machine shops), then valves with oversize stems must be fitted. Valves are usually available in 0.001 inch, 0.003 inch and 0.005 inch stem oversizes. Valve guides which are not excessively worn or distorted may, in some cases, be knurled rather than reamed. Knurling is a process in which the metal on the valve guide bore is displaced and raised, thereby reducing clearance. Knurling also provides excellent oil control. The option of knurling rather than reaming valve guides should be discussed with a reputable machinist or engine specialist.

Valve Lifters

-

.

» See Figures 114 and 115

REMOVAL & INSTALLATION 85773067

Fig. 113 Installing valve stem seals 2. Install the valves in the cylinder head, one at a time, as numbered. 3. Lubricate and position the seals and valve springs, again a valve at a time. 4. Install the spring retainers, and compress the springs. 5. With the valve key groove exposed above the compressed valve spring, wipe some wheel bearing grease around the groove. This will retain the keys as you release the spring compressor. 6. Using needle nose pliers (or your fingers), place the keys in the key grooves. The grease should hold the keys in place. Slowly release the spring compressor; the valve cap or rotator will raise up as the compressor is released, retaining the keys. 7. Install the rocker assembly, and install the cylinder head(s).

In-line 6 Cylinder

1. Disconnect the negative battery cable. 2. Remove the rocker arm cover. 3. Loosen the rocker arm until you can rotate it away from the pushrod or remove the rocker arm completely, giving clearance to the top of the pushrod. If the rocker arms do not need to be removed for other service procedures, it it easiest to leave the arm installed to the stud in order to prevent mixing them up during installation. 4. Remove the pushrod. If you are replacing all of the lifters, it is wise to make a pushrod holder as mentioned under

Cylinder Head Removal. This will help keep the pushrods in order, as they MUST go back in their original positions. 5. Remove the pushrod covers on the side of the block. 6. Remove the lifter(s). A hydraulic lifter removal tool (GM part No. J-3049 or equivalent) is available at dealers and most parts stores, and is quite handy for this procedure. A thin magnet may also be used in some cases to draw the lifters

VALVE ADJUSTMENTS All gasoline and diesel engines in this guide use hydraulic _ valve lifters, which require no periodic maintenance or adjustment. However, in the event of cylinder head removal or any operation that requires disturbing or removing the rocker arms, the rocker arms must be adjusted in order to position the pushrods to allow the hydraulic lifters to maintain zero lash. Refer to the valve lash adjustment procedure under Rocker Arms, earlier in this Section.

85773203

Fig. 114 Remove or reposition the rocker arm so the pushrod may be removed

3-54

ENGINE AND ENGINE REBUILDING 9. Properly adjust the valve lash or secure the rocker arm pivots, as applicable. 10. Install the valve covers, connect the spark plug wires and install the air cleaner. 8-379 Diesel

1. Disconnect the negative battery cable. 2. Remove the valve covers. 3. Remove the rocker shaft assemblies. 4. Remove the cylinder head(s). 5. Remove the guide clamps and guide plates. It may be necessary to use mechanical fingers to remove the guide plates. 6. Using GM tool No. J-29834 or another suitable lifter removal tool and a magnet, remove the lifter(s) through the access in the block. 7. Coat the lifters with clean engine oil before installation. If installing new lifters, they must be primed first by working the lifter plunger while the lifter is submerged in clean kerosene or diesel fuel. Lifters that have not been primed will seize when the engine is started. 8. Install the lifters in their original positions in the block. A lifter installation tool can be fabricated out of welding rod or similar gauge wire and may help. 9. Install the lifter guide plate and guide plate clamp. The crankshaft must be turned two full rotations (720 degrees) after assembly of the lifter guide plate clamp to insure free movement of the lifters in the guide plates.

73204

Fig. 115 With the pushrod removed, the lifters may be pulled from their bores upward so you can get your hands on them. Do not grab the outside of the lifters using a pair of pliers or any sharp instrument. 7. Before installing new lifters, all sealer coating must be removed from the inside. This can be done with kerosene or carburetor cleaning solvent. Also, the new lifters must be

_

primed before installation, as dry lifters will seize when the engine is started. Submerge the lifters in clean engine oil and work the lifter plunger up and down. 8. Install the lifter(s) and pushrod(s) into the cylinder block in their original positions. 9. Pivot the rocker arm back into its original position. With the lifter on the base circle of the camshaft (valve closed), tighten the rocker arm nut to 20 ft. los. Do not over torque. You will have to rotate the crankshaft to do the individual valves. 10. Replace the pushrod covers using new gaskets. Replace the.rocker arm cover, using a new gasket or sealer.

RETAINER RING OIL METERING VALVE

Gasoline V6, V8 and 350 Diesel

» See Figures 116 and 117

BALL

e>\alve lifters and pushrods should be kept in order so they can be reinstalled in their original position. Some engines will have both standard size and 0.010 inch oversize valve lifters as original equipment. The oversize lifters

LIFTER

BODY

BALL CHECK

= SPRING

CHECK

x

TNA aN »

es

PLUNGER

PUSH ROD SEAT

BALL CHECK RETAINER

are etched with an O on their sides; the cylinder block will

PLUNGER SPRING

also be marked with an O if the oversize lifter is used.

ROLLER 85773072

1. Remove the intake manifold and gasket. 2. Remove the valve covers, rocker arm assemblies and pushrods. 3. If the lifters are coated with varnish, apply carburetor

Fig. 116 Roller lifter, all 379 and 1981 350 diesel engines. 1980 250’s have a conventional lifter

cleaning solvent to the lifter body. The solvent should dissolve the varnish in about 10 minutes. 4. Remove the lifters. On diesels, remove the lifter retainer

guide bolts, and remove the guides. A special tool for removing lifters is available, and is helpful for this procedure. 5. New lifter MUST be primed before installation, as dry lifters will seize when the engine is started. Submerge the pee in clean engine oil and work the lifter plunger up and own. 6. Install the lifters and pushrods into the cylinder block in their original order. On diesels, install the lifter retainer guide. 7. Install the intake manifold gaskets and manifold. 8. Position the rocker arms, pivots and retainers on the cylinder head.

|

85773074

Fig. 117 Diesel valve lifter guide and retainer

ENGINE AND ENGINE REBUILDING RSP

EPS

SST

STS IPS BIH S OS

OTE RM

LE

TS

GSI

TACs

3-55 ETE

EE TG

10. Install the remainder of components in the reverse order of removal. e*The pushrods must be installed with their painted ends facing UP.

REMOVAL & INSTALLATION 6

In-line 6 Cylinder 1. Disconnect the negative battery cable. Raise the vehicle and support it safely. Drain the engine oil. 2. Remove the flywheel cover. Remove the starter assembly. 3. Remove the engine mount through bolts from the engine front mounts. Raise the engine enough to remove the oil pan. 4. Remove the oil pan retaining bolts. Remove the oil pan from the engine. 5. Installation is the reverse of the removal procedure. Use new gaskets or RTV sealant, as required. Torque the pan to front cover bolts to 45 inch Ibs. Torque the '/ in. pan to block bolts to 80 inch lbs. and the ‘6 in. bolts to 165 inch lbs.

Gasoline V8 and V6 Engines » See Figures 118, 119, 120 and 121

1. Disconnect the negative battery cable. Remove the air cleaner assembly, as required. Remove the distributor cap, if necessary. 2. Raise the vehicle and support it safely. Be sure to support the vehicle of jackstands at a sufficient height to allow ground clearance with the entire length of the oil pan as it will -have to be tilted almost vertically for removal. 3. Drain the engine oil, then remove the flywheel cover and the starter assembly. 4. On some vehicles equipped with V6 engine, remove the strut rods at the flywheel cover, as necessary. 5. On 4WD vehicles with automatic transmission, remove the strut rods at the engine mounts.

Fig. 119 Loosen and remove the oil pan bolts ele! a ratchet, extension and suitable socket d 6. On vehicles equipped with gauges, remove the oil pressure line from the side of the engine block to avoid damage when raising the engine. If necessary, remove the oil filter.

2 CAUTION Take extreme caution if the engine must be raised to remove the oil pan. Make sure the engine lift or hydraulic jack is firmly set. If at all possible, block the engine in this position using wooden blocks between the engine block or engine mounts and jackstands or the vehicle frame rail. 7. On most vehicles it will be necessary to raise the engine in order to gain clearance for oil pan removal. If necessary, carefully jack the engine slightly using a block of wood under the transmission tail Section or using a engine lift. If additional clearance is necessary, remove the engine mount through-bolts before raising the engine. Remove the oil pan retaining bolts. 8. Pivot the oil pan downward and the rear and carefully lower it from the engine. 9. Installation is the reverse of the removal procedure. Use new gaskets or RTV sealant, as required. On the V6 engine torque the pan retaining bolts to 100 inch lbs. On the small block V8 engines torque the bolts to 100 inch lbs. and the nuts to 200 inch lbs. On some 350 engines so equipped, torque the oil pan baffle bolts to 26 ft. lbs. On the 454 V8 engine torque the pan to front cover to 70 in. lbs and the pan

to block to 135 inch lbs.

85773207

73205

Fig. 118 The starter assembly and flywheel cover must be removed for access.

Fig. 120 Pivot the oi! pan rearward and begin to pull it down

sb Tit

356 ENGINE AND ENGINE REBUILDING mesh. Position the pump on the cap and install the attaching . bolts. 6. Install the oil pans on all engines.

Timing Chain Cover and Front Oil Seal REMOVAL & INSTALLATION 85773208

Fig. 121 Once the pan clears the engine and the lower crossmember you will be free to remove it from the vehicle

In-line 6 Cylinder

» See Figures 124, 125 and 126 1. Disconnect the negative battery cable.

Diesel Engines 1. Remove the vacuum pump and drive (with air conditioning) or the oil pump drive (without air conditioning). 2. Disconnect the batteries and remove the dipstick. 3. Remove the upper radiator support and fan shroud. 4..Raise and support the truck. Drain the oil. 5. Remove the flywheel cover. 6. Disconnect the exhaust and crossover pipes.

, 7. Remove the oil cooler lines at the filter base. "8 Remove the starter assembly. Support the engine with a 9,

Remove the engine mounts from the block.

3 > ~10. :Raise the front of the engine and remove the oil pan.

_,.11. Installation is the reverse of removal. On the 8-379 die___ sel engine torque all but the rear two. pan retaining bolts to 84 ~ _ in. lbs and the two rear bolts to 17 ft. lbs. On the 8-350 diesel ~ engine torque all pan retaining bolts to 10 ft. Ibs.

REMOVAL & INSTALLATION 70. Oil Pump . Baffle (Some 5.7L Engines) . Bolt . Nut (Some 5.7L Engines)

Gasoline and Diesel

» See Figures 122 and 123

. Gasket 75. Reinforcement

The oil pump is mounted to the bottom of the block and is accessible only by removing the oil pan. 1. On all engines, including diesel, remove the oil pan. 2. Unbolt and remove the oil pump and screen as an assembly. On the in-line sixes, remove the flange mounting bolts and nut from the elongated number 6 main bearing cap bolt, then remove the pump. To install: 3, Prime the pump with clean motor oil. 4. Align the oil pump drive shaft on the in-line 6 cylinder engines to match with the distributor tang and position the pump-flange over the distributor lower bushing. Install the

aR pp amp"mounting bolts. és iF ~ 5. On V6 and V8 engines, insert the drive shaft-extension ~~ through the opening in the main bearing cap until the shaft mates with the distributor drive gear. You may have to turn the drive shaft extension one way or the other to get the two to @

85773075

Fig. 122 Oil pump installation ORIVE SHAFT Ay

PUMP BODY IDLER

GEAR

ORIVE SHAFT DRIVE GEAR

SPRING RETAINING PIN

85773076

ENGINE AND ENGINE REBUILDING

3-57

Al

2. Drain the engine ‘coolant, remove the radiator hoses, and remove the radiator.

ck CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 3. Remove the fan belt and any accessory belts. Remove the fan pulley. 4. A harmonic balancer puller is necessary to pull the balancer. Install the puller and remove the balancer. 5., Remove the two screws which attach the oil pan to the front cover. Remove the screws which attach the front cover to the block. Do not remove the cover yet. 6. ‘Before the front cover is removed, it is necessary to cut the oil pan front seal. Pull the cover forward slightly. 7. Using a sharp knife or razor knife, cut the oil pan front seal flush with the cylinder block on both sides of the cover. 8. Remove the front cover and the attached portion of oil pan front seal. Remove the front cover gasket from the block. 9. To install the front cover, first obtain an oil pan front seal. Cut the tabs from the new seal. 10. Install the seal in the front cover, pressing the tips into the holes provided in the cover. Coat the mating area of the front cover with a room temperature vulcanizing (RTV) sealer first. 11. Coat the new front cover BE with sealer and install it on the cover. 12. Apply a ‘e inch bead of RTV sealer to iy ‘joint formed at the oil pan and cylinder block. » 13. Install the front cover. : 14. Install the harmonic balancer. Make sure the front cover seal is positioned evenly around the balancer. If you do not have access to a balancer installation tool (and you probably don’t) you can either fabricate one using the illustration as a guide, or you can tap the balancer on using a brass or plastic mallet. If you use the last method, make sure the balancer goes on evenly. 15. The rest of the installation is in the reverse order of removal. Gasoline V6 and V8s » See Figures 127, 128, 129, 130, 131, 132, 133, 134, 135 and 136

1. Disconnect the negative battery cable. 2. Drain the cooling system.

«CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove

85773077

Fig. 124 Applying sealer front cover mounting on the 250 in-line six

CUT THIS PORTION FROM NEW SEAL 85773078

os

85773079

Fig. 126 Cut the oil pan seal flush with the front of the block

fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. p> If the center crankshaft pulley bolt is difficult to remove, spray the bolt with penetrating oil and allow some time to work. Manual transmission vehicles may be placed in gear with an assistant holding the break pedal to give the resistance necessary to break loose the bolt. Automatic transmission vehicles are more difficult, first have

an assistant try to hold the pulley or use bolts threaded in % the outer holes to hold the pulley steady while the bolt is loosened. If this is not sufficient, a flywheel holding fixture

should be used to lock the crankshaft so the bolt may be removed.

. |

3-58

ENGINE AND ENGINE REBUILDING

85773209

85773213

Fig. 127 Remove the retaining bolt and remove the crankshaft pulley

Fig. 130 Remove the timing cover bolts from the cover flange

85773214

Fig. 128 Use a suitable damper puller to remove the crankshaft torsional damper. Do not use a jawed puller as it could damage the damper

Fig. 132 With the gasket seal broken, remove the cover from the front of the engine block 7. Apply sealer to the front cover as shown in the accompanying illustration. Install the cover carefully onto the locating dowels. 8. Tighten the attaching screws to 6-8 ft. Ibs. 9. Install the damper pulley using Tool J-23523 Damper Pulley installer and torque the retaining bolt to specifications. (See the Torque Specifications Chart). The damper may be installed by partially by hand and the bolt may be used to draw it into position if the fit is not too tight. If necessary, use some steel wool to clean the crankshaft-to-damper mating surfaces of corrosion and allow for a smoother fit.

85773215

Fig. 129 Once the damper is loosened, you should be able to pull it free by hand 3. Remove the crankshaft pulley and damper, using Tool J-23523 Damper Pulley remover and installer. Remove the water pump. Remove the screws holding the timing case cover to the block and remove the cover and gaskets. 4. Use a suitable tool to pry the old seal out of the front face of the cover. 5. Install the new seal so that the open end is toward the inside of the cover, using Tool J-35468 Seal installer.

8-350 Diesel

» See Figures 137 and 138 1. Disconnect the negative battery cable.

=>Coat the lip of the new seal with oil prior to installation. 6. Check that the timing chain oil slinger is in place against the crankshaft sprocket. 857732

Fig. 131 Once the bolts are removed, a small bit of leverage may be necessary to break the gasket seal f

ENGINE AND ENGINE REBUILDING

3-59

85773083

Fig. 136 Guiding front cover into place. Be careful seal remains in place

CHAMFER

85773084

85773212

Fig. 133 Be sure not to loose the rubber seal located on the bottom of most timing covers

Fig. 137 Grinding chamfer, 350 diesel dowel pin

TRIM 1/8" FROM EACH END OF PAN SEAL 85773085

85773081

Fig. 134 Seal installation with cover installed, V8’s

Fig. 138 Trimming pan seal with razor blade

2. Drain the cooling system and disconnect the radiator hoses.

sckCAUTION —

F

TRIM AN ASKET FLUSH WITH BLOCK “aT

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

D

85773082

Fig. 135 Sealer application

3-62

ENGINE AND ENGINE REBUILDING

Timing Chain and Sprockets REMOVAL & INSTALLATION (

Gasoline V8 and V6 » See Figures 144 and 145 1. Disconnect the negative battery cable. 2. Remove the radiator core.

i iN i

3. Remove the water pump.

4. Remove the harmonic balancer and the crankcase front cover. This will allow access to the timing chain. 5. Crank the engine until the timing marks on both sprockets are nearest each other and in line between the shaft

Peper

;

i

Peto

NG ; Fig. 144 V6 262 timing sprocket alignment

centers.

6. Take out the three bolts that hold the camshaft gear to the camshaft. This gear is a light press fit on the camshaft and will come off easily. On others it may require a puller. It is located by a dowel.The chain comes off with the camshaft ear. ; 7. A gear puller will be required to remove the crankshaft gear. To install: 8. Without disturbing the position of the engine, mount the new crankshaft gear on the shaft, and mount the chain over the camshaft gear. 9, Arrange the camshaft gear in such a way that the timing marks will line up between the shaft centers and the camshaft locating dowel will enter the dowel hole in the cam sprocket. 10. Place the cam sprocket, with its chain mounted over it, in position on the front of the car and pull up with the three bolts that hold it to the camshaft. After the gears are in place, turn the engine two full revolutions to make certain that the timing marks are in correct alignment between the shaft centers. e>When installing the timing chain, install the sprockets with the timing marks facing each other; this position is TDC of the No. 6 cyl. (V8) or No. 4 cyl. (V6). To locate the

TDC of the No. 1 cyl., turn the crankshaft one full revolution, the camshaft timing mark will now be at the top of

the sprocket.

8-350 Diesel

» See Figure 146 1. Disconnect the negative battery cable. 2. Remove the crankshaft pulley, the harmonic balancer and the front cover. 3. Align the timing marks on the cam and crankshaft. 4. Remove the oil slinger and camshaft sprocket retaining nut. 5. Remove the crankshaft sprocket. The sprocket-to-crankshaft fit is such that a puller may be necessary. If possible, the crankshaft key should be removed before using the puller. If this is not possible, align the puller so that the fingers of the tool do not overlap the end of the key when the sprocket is removed. The keyway is machined only part way in the crankshaft sprocket, and breakage can occur if the sprocket is improperly removed.

#6 CYLINDER ° AT T.D.C. 85773095

Fig. 145 Timing sprocket alignment, 1980 and later gasoline V8’s 6. Remove the timing chain and camshaft sprocket. To install: 7. The fuel pump eccentric is behind the crankshaft sprocket, and may be removed if necessary. 8. Install the key in the crankshaft, if removed. Install the fuel pump eccentric, if removed. 9. Install the camshaft sprocket, crankshaft sprocket and the timing chain together, with the timing marks aligned. Tighten the camshaft sprocket retaining bolt to 65 ft. Ibs.

e>When the two timing marks are in alignment and closest together, the No. 6 cylinder is at TDC. To obtain TDC for No. 1 cylinder, slowly rotate the crankshaft one full revolution. This will move the camshaft sprocket timing mark to the top. No. 1 cylinder will then be at TDC. 10. Install the oil slinger. 11. THE INJECTION PUMP MUST BE RE-TIMED. Refer to Section 2. 12. Install the front cover, harmonic balancer, and the crankshaft pulley.

8-379 Diesel

» See Figure 147 1. 2. 3. gear.

Disconnect the negative battery cable. Remove the front cover. Remove the bolt and washer attaching the camshaft Remove the injection pump gear.

4, Remove the camshaft sprocket, timing chain, and crank-

shaft sprocket as a unit.

ENGINE AND ENGINE REBUILDING

3-63

CAM SPROCKET

CRANK

SPROCKET 85773098

Fig. 147 379 diesel timing chain assembly

85773097

Fig. 146 350 diesel timing sprocket alignment

To install: 5. Install, the cam sprocket, timing chain and crankshaft sprocket as a unit, aligning the timing marks on the sprockets as shown in the illustration. 6. Rotate the crankshaft 360 degrees so that the camshaft gear and the injection pump gear are aligned as shown in the illustration (accompanying the 379 Diesel Front Cover Removal Procedure). 7. Install the front cover. The injection pump must be retimed since the timing chain assembly was removed. See Section 2 for this procedure.

6. Remove the two camshaft thrust plate retaining screws by working through the holes in the camshaft gear. 7. Remove the camshaft and gear assembly by pulling it out through the front of the block. 8. If either the camshaft or the camshaft gear is being renewed, the gear must be pressed off the camshaft. The replacement parts must be assembled in the same way. When placing the gear on the camshaft, press the gear onto the shaft until it bottoms against the gear spacer ring. The end clearance of the thrust plate should be 0.001 — 0.005 inch. 9. Pre-lube the camshaft lobes with clean engine oil and then install the camshaft assembly in the engine. Be careful not to damage the bearings. 10. Turn the crankshaft and the camshaft gears so that the timing marks align. Push the camshaft into position and install and torque the thrust plate bolts to 7 ft. Ibs. 11. Check camshaft and crankshaft gear run-out with a dial indicator. Camshaft gear run-out should not exceed 0.004 inch and crankshaft gear run-out should not be above 0.003 inch. 12. Using a dial indicator, check the backlash at several points between the camshaft and crankshaft gear teeth. Backlash should be 0.004-0.006 inch. 13. Install the timing gear cover. Install the harmonic balancer. 14. Install the valve lifters and the pushrods. Install the side cover. Install the coil and the fuel pump. 15. Install the distrioutor and set the timing. Pivot the rocker . arms over the pushrods and adjust the valves. 16. Install the radiator, hoses and grille.

REMOVAL & INSTALLATION

Gasoline V6 and V8

» See Figures 149 and 150 1. Disconnect the negative battery cable.

» See Figure 148

2. Drain and remove the radiator.

In-line 6 Cylinder

«CAUTION

1. Remove the grille. Remove the radiator hoses and remove the radiator. 2. Remove the timing gear cover. 3. Remove the valve cover and gasket, loosen all the rocket arm nuts, and pivot the rocker arms clear of the pushrods. 4, Remove the distributor and the fuel pump. 5. Remove the pushrods. Remove the coil and then remove the side cover. Remove the valve lifters.

When draining the coolant, keep in mind that cats and

dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

3. Disconnect the fuel line at the fuel pump. Remove the pump.

3-64

ENGINE AND ENGINE REBUILDING

85773217

Fig. 150 Slowly turn the camshaft as you remove it from the engine

85773100

Fig. 148 Removing camshaft. Slowly turn the cam as you remove it 4. Disconnect the throttle cable and the air cleaner. 5. Remove the alternator belt, loosen the alternator bolts and move the alternator to one side. 6. Remove the power steering pump from its brackets and move it out of the way. 7. It may be necessary on some models, to remove the air conditioning compressor from its brackets and move the compressor out of the way without disconnecting the lines. 8. Disconnect the hoses from the water pump. 9. Disconnect the electrical and vacuum connections. 10. Mark the distributor as to location in the block. Remove the distributor.

Fig. 149 The camshaft timing gear bolts may be grasped and used to pull the camshaft from the engine block

11. Raise the car and drain the oil pan. 12. Remove the exhaust crossover pipe and starter motor. 13. Disconnect the exhaust pipe at the manifold. 14. Remove the harmonic balancer and pulley. 15. Support the engine and remove the front motor mounts. 16. Remove the flywheel inspection cover. 17. Remove the engine oil pan. 18. Support the engine. 19. Remove the engine front cover. 20. Remove the valve covers. 21. Remove the intake manifold, oil filler pipe, and temperature sending switch. 22. Mark or assort the lifters, pushrods, and rocker arms as

to location so that they may be installed in the same position. Remove these parts. 23. If the car is equipped with air conditioning, discharge the air conditioning system, see Section 1, and remove the condenser. 24. Remove the fuel pump eccentric, camshaft gear, oil slinger, and timing chain. Remove the camshaft thrust plate on front of camshaft, if equipped. 25. Carefully remove the camshaft from the engine pulling straight backwards to avoid journal or bearing damage. The camshaft timing gear bolts may be used as a grip to pull the camshaft from the block. 26. Inspect the shaft for signs of excessive wear or damage. 27. Liberally coat camshaft and bearings with heavy engine oil or engine assembly lubricant and insert the cam into the engine. 28. Align the timing marks on the camshaft and crankshaft gears. See Timing Chain Replacement for details. 29. Install the distributor using the locating marks made during removal. If any problems are encountered, see Distributor Installation. 30. Install the remainder of the parts in the reverse of above but pay attention to the following points: a. Install the timing indicator before installing the power steering pump bracket. b. Install the flywheel inspection cover after installing the starter. c. Replace the engine oil and ‘radiator coolant.

ENGINE AND ENGINE REBUILDING ‘SE SS

SRR

SSS

AD

ASS SESE OS

TS

SSR

TSS

aS

ETS

SS

SSS

ES

3-65

SOS

SE

BEDS

8-350 Diesel » See Figures 151 and 152 hee uta

dures. Failure to bleed down the lifters could bend valves when the engine is turned over. 18. Install the injection pump adapter and injection pump.

discharged by an air conditioning specialist before the

procedures.

-lf equipped with air conditioning, the system must be camshaft is removed. The condenser must also be re-

See the appropriate Sections under Fuel System above for 19. Install the remaining components in the reverse order of

moved from the car. Removal of the camshaft also requires removal of the injection pump drive and driven

removal

gears, removal of the intake manifold, disassembly of the valve lifters, and retiming of the injection pump.

8-379 Diesel REMOVAL

1. Disconnect the negative battery cables. 2. Remove the intake manifold and gasket and the front and rear intake manifold seals. Refer to the intake manifold removal and installation procedure.

1. Disconnect both batteries. 2. Jack up the truck and safely support it with jackstands.

3. Remove the balancer pulley and the balancer. Remove

the engine front cover. 4. Remove the valve covers. Remove the rocker arms, pushrods and valve lifters. Be sure to keep the parts in order so that they may be returned to their original positions. 5. Remove the camshaft sprocket retaining bolt, and remove the timing chain and sprockets, using the procedure outlined earlier. 6. Position the camshaft dowel pin at the 3 o'clock position. 7. Push the camshaft rearward and hold it there, being careful not to dislodge the oil gallery plug at the rear of the engine. Remove the fuel injection pump drive gear by sliding it from the camshaft while rocking the pump driven gear. 8. To remove the fuel injection pump driven gear, remove the pump adapter, the snapring, and remove the selective washer. Remove the driven gear and spring. 9. Remove the camshaft by sliding it out the front of the engine. Be extremely careful not to allow the cam lobes to contact any of the bearings, or the journals to dislodge the bearings during camshaft removal. Do not force the camshaft, or bearing damage will result. 10. If either the injection pump drive or driven gears are to

CUP PLUG

OIL GALLERY PLUG

7

CAMSHAFT VE END, PLUG 85773101

Fig. 151 Camshaft and oil gallery plugs at rear of block

be replaced, replace both gears.

OE eR

11. Coat the camshaft and the cam bearings with a heavy weight engine oil, GM lubricant No. 1052365 or the equivalent.

65 FT. LBs. eae

12. Carefully slide the camshaft into position in the engine.

13. Fit the crankshaft and camshaft sprockets, aligning the

timing marks as shown in the timing chain removal and installation procedure, above. Remove the sprockets without disturbing the timing. 14. Install the injection pump driven gear, spring, shim, and snapring. Check the gear end-play. If the end-play is not within 0.002-0.015 inch, replace the shim to obtain the specified clearance. Shims are available in 0.003 inch increments, from

;

EIR cur nie AY

Afal

LBS.

.

}

INJECTION PUMP DRIVE

GEAR PUSH CAM AGAINST

eS

weSin

POSITION AT

paces

comet CANS HAET-SPROCEE!

ay. ON TIMING CHAIN

A UES ENGINE TIMING INDICATOR

SoUtsty2

0.080 inch to 0.115 inch. 15. Position the camshaft dowel pin at the 3 o'clock position. Align the ‘zero' marks on the pump drive gear and pump driven gear. Hold the camshaft in the rearward position and slide the pump drive gear onto the camshaft. Install the camshaft bearing retainer. 16. Install the timing chain and sprockets, making sure the timing marks are aligned. 17. Install the lifters, pushrods and rocker arms. See Rocker Arm Replacement, Diesel Engine for lifter bleed down proce-

Fig. 152 350 diesel injection pump drive gear installation

3-66

ENGINE AND ENGINE REBUILDING

3. Drain the cooling system, including the block.

“CAUTION

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. 4. Disconnect the exhaust pipes at the manifolds. Remove the fan shroud. 5. Lower the truck. 6. Remove the radiator and fan. 7. Remove the vacuum pump and the intake manifold. 8. Remove the injection pump and lines as outlined in Section 5. Make sure you cap all injection lines to prevent dirt from entering the system, and tag the lines for later installation. 9. Remove the water pump. 10. Remove the injection pump drive gear. 11. Scribe a mark aligning the line on the injection pump flange to the front cover. 12. Remove the injection pump from the cover. 13. Remove the power steering pump and the generator and lay them aside. 14. If the truck is equipped with air conditioning, remove the compressor (with the lines attached) and position it out of the way.

«CAUTION DO NOT disconnect the air conditioning lines unless you are familiar with this procedure. Refer to Section 1 “Air Conditioning”. 15. Remove the valve covers. 16. Remove the rocker shaft assemblies and pushrods. Place the pushrods in order in a rack (easily by punching holes in a piece of heavy cardboard and numbering the holes) so that they can be installed in correct order. 17. Remove the thermostat housing and the crossover from the cylinder heads. 18. Remove the cylinder heads , with the exhaust manifolds attached. 19. Remove the valve lifter clamps, guide plates and valve lifters. Place these parts in a rack so they can be installed in the correct order. 20. Remove the front cover. 21. Remove the timing chain assembly. 22. Remove the fuel pump. 23. Remove the camshaft retainer plate. 24. If the truck is equipped with air conditioning, remove the air conditioning condenser mounting bolts. Have an assistant help in lifting the condenser out of the way. eh Remove the camshaft by carefully sliding it out of the

ock.

INSTALLATION

Whenever a new camshaft is installed, GM recommends replacing all the valve lifters, as well as the oil filter. The engine

oil must be changed. These measures will help ensure proper wear characteristics of the new camshaft. 1. Coat the camshaft lobes with Molykote or an equivalent lube. Liberally lube the camshaft journals with clean engine oil and install the camshaft carefully. 2. Install the camshaft retainer plate and torque the bolts to 20 ft. Ibs. 3. Install the fuel pump. 4. Install the timing chain assembly. 5. Install the front cover. 6. Install the valve lifters, guide plates and clamps. Rotate the crankshaft as previously outlined so that the lifters are free to travel. 7. Install the cylinder heads. 8. Install the pushrods in their original order. Install the rocker shaft assemblies, then install the valve covers.

9. Install the injection pump to the front cover, making sure the lines on the pump and the scribe line on the front cover are aligned. 10. Install the injection pump driven gear, making sure the gears are aligned. Re-time the injection pump. 11. Install the remaining engine components in the reverse order of removal. Make the necessary adjustments (drive belts, etc.) and refill the cooling system.

CAMSHAFT INSPECTION Completely clean the camshaft with solvent, paying special attention to cleaning the oil holes. Visually inspect the cam lobes and bearing journals for excessive wear. If a lobe is questionable, have the cam checked at a reputable machine shop; if a journal or lobe is worn, the camshaft must be reground or replaced. Also have the camshaft checked for straightness on a dial indicator.

elf a cam journal is worn, there is a good chance that the bushings are worn.

Camshaft Bearings REMOVAL & INSTALLATION » See Figures 153, 154 and 155 If excessive camshaft wear is found, or if the engine is being completely rebuilt, the camshaft bearings should be replaced.

eThe front and rear bearings should be removed last, and installed first. Those bearings act as guides for the other bearings and pilot.

1. Drive the camshaft rear plug from the block. 2. Assemble the removal puller with its shoulder on the bearing to be removed. Gradually tighten the puller nut until the bearing is removed. :

:

ENGINE AND ENGINE REBUILDING

3-67

degree bend in the end as shown in the illustration. Check all oil hole openings; the wire must enter each hole, or the

hole is not properly aligned. 5. Replace the camshaft rear plug, and stake it into position. On the 379 diesel, coat the outer diameter of the new plug with GM sealant No. 1052080 or equivalent, and install it

flush to '/s2 inch deep.

Pistons and Connecting Rods 85773103

PISTON REMOVAL

Fig. 153 Camshaft bearing removal and installation tool » See Figures 156, 157, 158, 159, 160 and 161

c=

85773104

Fig. 154 Installing front cam bearing on 379 diesel. Bearing tool is illustrated inset. Method is similar on other engines

CHECKING O/L HOLE ALIGNMENT WITH BRASS ROD. MAKE ROD SHOWN USING 3/32 BRASS ROD

_ Before removing the pistons, the top of the cylinder bore must be examined for a ridge. A ridge at the top of the bore is the result of normal cylinder wear, caused by the piston rings only traveling so far up the bore in the course of the piston stroke. The ridge can be felt by hand; it must be removed before the pistons are removed. A ridge reamer is necessary for this operation. Place the piston at the bottom of its stroke, and cover it with a rag. Cut the ridge away with the ridge reamer, using extreme care to avoid cutting too deeply. Remove the rag, and remove the Cuttings that remain on the piston with a magnet and a rag soaked in clean oil. Make sure the piston top and cylinder bore are absolutely clean before moving the piston. 1. Remove intake manifold and cylinder head or heads. 2. Remove oil pan. 3. Remove oil pump assembly if necessary. 4, Matchmark the connecting rod cap to the connecting rod with a scribe; each cap must be reinstalled on its proper rod in the proper direction. Remove the connecting rod bearing cap and the rod bearing. Number the top of each piston with silver paint or a felt-tip pen for later assembly. 5. Cut lengths of 4 inch diameter hose to use as rod bolt guides. Install the hose over the threads of the rod bolts, to

85773105

Fig. 155 Make this simple tool to check camshaft bearing oil alignment 3. Remove the remaining bearings, leaving the front and rear for last. To remove these, reverse the position of the puller, so as to pull the bearings towards the center of the block. Leave the tool in this position, pilot the new front and rear bearings on the installer, and pull them into position. 4. Return the puller to its original position and pull the remaining bearings into position. >You must make sure that the oil holes of the bearings and block align when installing the bearings. If they don’t align, the camshaft will not get proper lubrication and may seize or at least be seriously damaged. To check for correct oil hole alignment, use a piece of brass rod with a 90

prevent the bolt threads from damaging the crankshaft journals and cylinder walls when the piston is removed. 6. Squirt some clean engine oil onto the cylinder wall from above, until the wall is coated. Carefully push the piston and rod assembly up and out of the cylinder by tapping on the bottom of the connecting rod with a wooden hammer handle. 7. Place the rod bearing and cap back on the connecting rod, and install the nuts temporarily. Using a number stamp or punch, stamp the cylinder number on the side of the connecting rod and cap; this will help keep the proper piston and rod assembly on the proper cylinder. >On V6 engines, starting at the front the cylinders are numbered 2-4-6 on the right bank and 1-3-5 on the left. On all V8s, starting at the front the right bank cylinders are 2-4-6-8 and the left bank 1-3-5-7. 8. Remove remaining pistons in similar manner. On all gasoline engines, the notch on the piston will face the front of the engine for assembly. The chamfered corners of the bearing caps should face toward the front of the left bank and toward the rear of the right bank, and the boss on the con-

3-68

ENGINE AND ENGINE REBUILDING

necting rod should face toward the front of the engine for the right bank and to the rear of the engine on the left bank. On the 350 diesel, install each piston and rod in its respective cylinder bore so the valve depression in the top of the piston is towards the inner side of the engine. On the forward half of the engine (cylinders 1, 2, 3, 4) the large valve depression goes to the front. On the rear half, the large valve depression goes to the rear. On the 379 diesel, install the piston and rod assemblies with the rod bearing tang slots on the side opposite the camshaft. On various engines, the piston compression rings are marked with a dimple, a letter T, a letter O, GM or the word TOP to identify the side of the ring which must face toward the top of the piston.

85773108

Fig. 158 Match the connecting rods to their cylinders with a number stamp

PISTON RING AND WRIST PIN REMOVAL » See Figures 162, 163, 164, 165, 166, 167, 168, 169, 170, 171 and 172 Some of the engines covered in this guide utilize pistons with pressed-in wrist pins; these must be removed by a special press designed for this purpose. Other pistons have their wrist pins secured by snaprings, which are easily removed with snapring pliers. Separate the piston from the connecting rod. A piston ring expander is necessary for removing piston rings without damaging them; any other method (screwdriver blades, pliers, etc.) usually results in the rings being bent, scratched or distorted, or the piston itself being damaged. When the rings are removed, clean the ring grooves using an

85773109

Fig. 159 Connecting rod bolt guide

RIDGE CAUSED BY CYLINDER WEAR

85773110 85773106

Fig. 156 Ridge formed by piston rings at the top of their travel

Fig. 160 Push the piston and rod out with a hammer handle appropriate ring groove cleaning tool, using care not to cut too deeply. Thoroughly clean all carbon and varnish from the piston with solvent.

Do not use a wire brush or caustic solvent (acids, etc.) on pistons. SSS

85773107

Fig. 157 Match the connecting rods to their caps with a scribe mark

SSS

Inspect the pistons for scuffing, scoring, cracks, pitting, or excessive ring groove wear. If these are evident, the piston must be replaced. The piston should also be checked in relation to the cylinder diameter. Using a telescoping gauge and micrometer, or a dial gauge, measure the cylinder bore diameter perpendicular (90

ENGINE AND ENGINE REBUILDING

3-69

NOTCH TO geaie OF ENGINE

PISTON AND CONNECTING ROD. INSTALL IN CYLINDER BORES 6, %, #7 & #8

OIL SPURT HOLE TOWARD CAMSHAFT SIDE OF ENGINE

HEAVY SIDE OF ROD RING TO FRONT OF ENGINE

85773112

Fig. 162 250 and 292 six cylinder piston and rod positioning

NOTCH TO FRONT OF ENGINE “F’ TOWARD FRONT

DEPRES SION CONNECTING ROD BEARING CONNECTING PISTON AND CONNECTING ROD CAP ROD. INSTALL IN CYLINDER BORES #), #2, 3&4 85773111

85773113

Fig. 161 350 diesel piston positioning degree) to the piston pin, 2'/2 inch below the cylinder block deck (surface where the block mates with the heads). Then, with the micrometer, measure the piston perpendicular to its wrist pin on the shirt. The difference between the two measurements is the piston clearance. If the clearance is within specifications or slightly below (after the cylinders have been bored or honed), finish honing is all that is necessary. If the clearance is excessive, try to obtain a slightly larger piston to bring clearance to within specifications. If this is not possible, obtain the first oversize piston and hone (or if necessary, bore) the cylinder to size. Generally, if the cylinder bore is tapered 0.005 inch or more or is out-of-round 0.003 inch or more it is advisable to rebore for the smallest possible over size piston and rings. After measuring, mark pistons with a felt-tip pen for reference and for assembly.

Fig. 163 Small block V8 piston and rod positioning, V6 similar VALVE CLEARANCE DEPRESSION TO CENTER OF CYLINDER BLOCK

BEARING TANG OPPOSITE CAMSHAFT

BEARING TANG OPPOSITE CAMSHAFT 85773114

Fig. 164 Big block V8 piston and rod positioning

s>Cylinder honing and/or boring should be performed by a reputable, professional mechanic with the proper equipment. In some cases, clean-up honing can be done with the cylinder block in the car, but most excessive honing and all cylinder boring must be done with the block stripped and removed from the car.

that the rings and the top 2 inch of cylinder wall are coated. Using an inverted piston, press the rings approximately 1 inch below the deck of the block (on diesels, measure ring gap clearance with the ring positioned at the bottom of ring travel in the bore). Measure the ring end gap with a feeler gauge, and compare to the Ring Gap chart in this Section. Carefully pull the ring out of the cylinder and file the ends squarely with a fine file to obtain the proper clearance.

Piston Ring End Gap » See Figures 173, 174 and 175

Piston Ring Side Clearance Check and Installation » See Figures 176 and 177

Piston ring end gap should be checked while the rings are removed from the pistons. Incorrect end gap indicates that the wrong size rings are being used; ring breakage could occur. Compress the piston rings to be used in a cylinder, one at a time, into that cylinder. Squirt clean oil into the cylinder, so

Check the pistons to see that the ring grooves and oil return holes have been properly cleaned. Slide a piston ring into its

groove, and check the side clearance with a feeler gauge. On

3-70

ENGINE AND ENGINE REBUILDING ET

AS COMPRESSION RING

secon

COMPRESSION RING

RING GROOVE CLEANER

;

EXPANDER

oe

85773118

Fig. 168 Clean the piston ring grooves using ring groove cleaner

85773115 85773119

Fig. 165 Piston ring and wrist pin assembly, 350 diesel shown. Gasoline engines similar

Fig. 169 Measuring the piston prior to fitting

—>— CENTERLINE

RING

EXPANDER 85773116

;

OF ENGINE

A—AT RIGHT ANGLE TO CENTERLINE OF ENGINE B—PARALLEL TO CENTERLINE OF ENGINE 85773120

Fig. 170 Cylinder bore measuring points

85773117 85773121

Fig. 167 Install the piston lock-rings, if used

Fig. 171 Measuring cylinder bore with a dial gauge

ENGINE AND ENGINE REBUILDING 3-71

4 ENGINE

LEFT

ENGINE

FRONT

ENGINE

1-3-5

rout [>

CYLINDER

85773122

Fig. 172 Cylinder bore cross-hatching after honing 2-4-6

CYLINDER

St RR

“A” OIL RING SPACER GAP (Tang In Hole or Slot within Arc) “B" OIL RING

“C'" 2ND

RAIL GAPS

COMPRESSION

RING GAP

“DB” TOP COMPRESSION

RING GAP 85773125

85773123

Fig. 173 Checking piston ring end gap with a feeler gauge

Fig. 175 V6 262 ring gap location

PISTON RING

FEELER GAUGE

@ enone LertSone Bone erane att

2-4-6-8 cyl.

RING

GROOVE

* 85773126

Fig. 176 Checking piston ring side clearance

“SMALL V8"

“A” OIL RING SPACER GAP (Tang in Hole or Slot within Arc)

“B" OIL RING RAIL GAPS “C” 2ND COMPRESSION RING CAP “D” TOP COMPRESSION RING GAP 85773124

Fig. 174 Ring gap location-all gasoline engines

gasoline engines, make sure you insert the gauge between the ring and its lower land (lower edge of the groove), because any wear that occurs forms a step at the inner portion of the lower land. On diesels, insert the gauge between the ring and the upper land. If the piston grooves have worn to the extent that relatively high steps exist on the lower land, the piston should be replaced, because these will interfere with the operation of the new rings and ring clearances will be excessive. Piston rings are not furnished in oversize widths to compensate for ring groove wear. Install the rings on the piston, lowest ring first, using a piston ring expander. There is a high risk of breaking or distorting the rings, or scratching the piston, if the rings are installed by hand or other means.

3-72 ENGINE AND ENGINE REBUILDING dik rieedeanaetibaieeeiemicbiestareimminOnaariS Ek Position the rings on the piston as illustrated; spacing of the various piston ring gaps is crucial to proper oil retention and even cylinder wear. When installing new rings, refer to the installation diagram furnished with the new parts.

CONNECTING ROD BEARINGS » See Figures 178, 179, 180 and 181 Connecting rod bearings for the engines covered in this guide consist of two halves or shells which are interchangeable in the rod and cap. When the shells are placed in position, the ends extend slightly beyond the rod and cap surfaces so that when the rod bolts are torqued the shells will be clamped tightly in place to insure positive seating and to prevent turning. A tang holds the shells in place.

the top or bottom of each crank journal. The Plastigage® has a range of 0.001-0.003 inch. 1. Remove the rod cap with the bearing shell. Completely clean the bearing shell and the crank journal, and blow any oil from the oil hole in the crankshaft; Plastigage® is soluble in oil. 2. Place a piece of Plastigage® lengthwise along the bottom center of the lower bearing shell, then install the cap with shell and torque the bolt or nuts to specification. DO NOT turn the crankshaft with Plastigage® in the bearing. 3. Remove the bearing cap with the shell. The flattened Plastigage® will be found sticking to either the bearing shell or crank journal. Do not remove it yet. 4. Use the scale printed on the Plastigage® envelope to measure the flattened material at its widest point. The number

->The ends of the bearing shells must never be filed flush with the mating surface of the rod and cap. lf a rod bearing becomes noisy or is worn so that its clearance on the crank journal is sloppy, a new bearing of the correct undersize must be selected and installed since there is a provision for adjustment.

>< WARNING Under no circumstances should the rod end or cap be filed to adjust the bearing clearance, nor should shims of

any kind be used.

85773218

Fig. 178 Apply a strip of Plastigage® or equivalent material across the bearing

Inspect the rod bearings while the rod assemblies are out of the engine. If the shells are scored or show flaking, they should be replaced. If they are in good shape check for proper clearance on the crank journal (see below). Any scoring or ridges on the crank journal means the crankshaft must be replaced, or reground and fitted with undersized bearings. Checking Bearing Clearance and Replacing Bearings e>Make sure connecting rods and their caps are kept together, and that the caps are installed in the proper direction. Replacement bearings are available in standard size, and in undersizes for reground crankshafts. Connecting rod-to-crankshaft bearing clearance is checked using Plastigage® at either

85773219

Fig. 179 Install and torque the bearing to specification

ENDS-OIL CONT. RING SPACER

¢ PISTON PIN

85773220 85773127

Fig. 177 379 diesel piston ring gap positioning

Fig. 180 Remove the bearing and compare the width of the line to the scale supplied in the kit

ENGINE AND ENGINE REBUILDING within the scale which most closely corresponds to the width of the Plastigage® indicates bearing clearance in thousandths of an inch. 5. Check the specifications chart in this Section for the desired clearance. It is advisable to install a new bearing if clearance exceeds 0.003 inch; however, if the bearing is in good condition and is not being checked because of bearing noise, bearing replacement is not necessary. 6. If you are installing new bearings, try a standard size, then each undersize in order until one is found that is within the specified limits when checked for clearance with Plastigage®. Each undersize shell has its size stamped on it. 7. When the proper size shell is found, clean off the Plastigage®, oil the bearing thoroughly, reinstall the cap with its shell and torque the rod bolt nuts to specification. m>With the proper bearing selected and the nuts torqued, it should be possible to move the connecting rod back and forth freely on the crank journal as allowed by the specified connecting rod end clearance. If the rod cannot be moved, either the rod bearing is too far undersize or the rod is misaligned.

PISTONS & CONNECTING ROD ASSEMBLY AND INSTALLATION » See Figures 182, 183, 184 and 185

Install the connecting rod to the piston, making sure piston installation notches and any marks on the rod are in proper relation to one another. Lubricate the wrist pin with clean engine oil, and install the pin into the rod and piston assembly, either by hand or by using a wrist pin press as required. Install snaprings if equipped, and rotate them in their grooves to make sure they are seated. To install the piston and connecting rod assembly: 1. Make sure connecting rod bearings (including end cap) are of the correct size and properly installed. 2. Fit rubber hoses over the connecting rod bolts to protect the crankshaft journals. Coat the rod bearings with clean oil. 3. Using the proper ring compressor, insert the piston assembly into the cylinder so that the notch in the top of the piston faces the front of the engine (this assumes that the dimple(s) or other markings on the connecting rods are in correct relation to the piston notch(es).

FLATTENED GAGING PLASTIC 85773128

Fig. 181 Checking rod bearing clearance with Plastigage® or equivalent

RING

3-73

COMPRESSOR 85773130

Fig. 182 Using a wooden hammer handle, tap the piston down through the ring compressor and into the cylinder 4. clean place, 5.

From beneath the engine, coat each crank journal with oil. Pull the connecting rod, with the bearing shell in into position against the crank journal. Remove the rubber hoses. Install the bearing cap and

cap nuts and torque to specification.

e>When more than one rod and piston assembly is being installed, the connecting rod cap attaching nuts should only be tightened enough to keep each rod in position until all have been installed. This will ease the installation of the remaining piston assemblies. 6. Check the clearance between the sides of the connecting rods and the crankshaft using a feeler gauge. Spread the rods slightly with a screwdriver to insert the gauge. If clearance is below the minimum tolerance, the rod may be machined to provide adequate clearance. If clearance is excessive, substitute an unworn rod, and recheck. If clearance is still outside specifications, the crankshaft must be welded and reground, or replaced. 7. Replace the oil pump, if removed, and the oil pan. 8. Install the cylinder head(s) and intake manifold.

Freeze Plugs REMOVAL & INSTALLATION 1. Disconnect the negative battery cable.

85773221

Fig. 183 Coat the bearings with clean engine oil before installation

3-74

ENGINE AND ENGINE REBUILDING 4. Remove any components that restrict access to the freeze plugs, like the starter or motor mounts. 5. Wearing proper eye protection, tap the bottom edge of the freeze plug with a chisel. This should tilt the freeze plug, not cut it. Then use pliers to pull or pry the freeze plug from its bore. Another method is to drill the freeze plug and use a slide hammer, but more often there’s not enough room to do that. 6. After the plug is removed clean the area completely. Coat the freeze plug and/or bore with gasket sealant. 7. Install the freeze plug into the hole, it must go in evenly or it will keep popping back out as you tap on it. Using a plug installer or socket that fits the edge of the plug can help keep it straight as you tap it in place. 8. Fill the engine with coolant, connect the battery cable. Start engine and check for leaks.

2 3==

Samer

pea

85773222

Fig. 184 Checking rod side clearance using a feeler gauge

Block Heater

|

REMOVAL & INSTALLATION Factory Installed Block Heater 1. Disconnect the negative battery cable.

>kCAUTION | When draining the coolant, keep in mind that cats and

dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a

sealable container. Coolant should be reused unless it is contaminated or several years old.

85773131

Fig. 185 Checking connecting rod side clearance with a feeler gauge. Use a small pry to carefully spread the connecting rods 2. Drain the cooling system.

CAUTION

|

When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old. ES

EELS

TE TN PSSST

ONE EE SBSSIE

SENET

NETIC

IE SIE RIES ISTE

SESS

ESSELTE

SSE

SES

3. If equipped with drain plugs on the engine remove them. They would be located at the bottom of the block near the oil pan.

2. Drain the coolant. 3. Remove all necessary items in order to gain access to the block heater. 4. Disconnect the block heater and bring the harness to an easily removable position. 5. Loosen the retaining screw and remove the block heater from the engine. To install: 6. Spread water-proof sealant on the outside perimeter of the block heater. 7. Install the unit squarely into its bore. 8. Install all removed items. 9. Fill the cooling system. Start the engine and check for leaks. Aftermarket Block Heater

If an aftermarket heater has been installed the following procedure will most likely work. There are two basic types, one for the oil and one for the coolant. The oil heater usually just slips into the dipstick tube or replaces the oil drain plug. The following procedure is for the coolant type. 1. Remove the negative battery cable.

ENGINE AND ENGINE REBUILDING

3-75

2. Drain the cooling system.

2 CAUTION When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is -contaminated or several years old. 3. Remove the block heater in the same way as the freeze plugs. Some heater units have a bolt that must be loosened or a V-Clamp that must be removed to remove the heating element. . 4. Diséonnect the heater connector and remove the heater element. 5. Coat the new heater with sealant: and install as removed. 6. Fill the engine with coolant, connect the battery cable. Start engine and check for leaks.

85773133

Fig. 187 Removing the upper seal half from the block

DUST SEAL

Rear Main Oil Seal REMOVAL & INSTALLATION 85773134

» See Figures 186, 187, 188, 189 and 190

Fig. 188 Rear main seal half, bearing cap side

In-line 6 Cylinder The rear main bearing oil seal, both halves, can be removed without removal of the crankshaft. Always replace the upper and lower halves together. 1. Remove the oil pan. 2. Remove the rear main bearing cap. 3. Remove the old oil seal from its groove in the cap, prying from the bottom using a small screwdriver. 4. Coat a new seal half with clean engine oil, and insert it into the bearing cap groove. Keep oil off of the parting line surface, as this surface is treated with glue. Gradually push

the seal place. 5. To hammer out until

with a hammer handle until the seal is rolled into remove the upper half of the old seal, use a small and a soft, blunt punch to tap one end of the oil seal it protrudes far enough to be removed with needle

85773135

? 85773132

Fig. 186 Remove the seal half from the bearing cap without scratching the cap

Fig. 189 Make a real main bearing seal packing tool from a wooden dowel. The upper tool dimensions are for engines up to 400 cu. in; the bottom is for 454’s

3-76

ENGINE AND ENGINE REBUILDING 10. Using the fabricated tool as a shoe horn, to protect the

seal’s bead from the sharp edge of the seal seat surface in the cylinder case, roll the seal around the crankshaft. when the seal’s ends are flush with the engine block, remove the

installation. 11. Using the same manner of installation, install the lower

half onto the lower half of the rear main bearing cap. 12. Apply sealant to the cap-to-case mating surfaces and install the lower rear main bearing half to the engine; keep the sealant off of the seal’s mating line. 13. Install the rear main bearing cap bolts and torque to 10-12 ft. lbs. Using a lead hammer, tap the crankshaft forward and rearward, to line up the thrust surfaces. Torque the main bearing bolts to 70-85 ft. Ibs. (V6 and V8) or 60-75 ft. Ibs. (inline 6 cylinder) and reverse the removal procedures. Refill the crankcase. 1986-88 MODELS (One Piece Seal) » See Figures 191, 192 and 193 Y)

FLy

1

85773136

Fig. 190 Packing the oil seal nose pliers. Push the new seal into place with the lip toward the front of the engine. 6. Install the bearing cap and torque the bolts to a loose fit — do not final torque. With the cap fitted loosely, move the crankshaft first to the rear and then to the front with a rubber mallet. This will properly position the thrust bearing. Torque the bearing cap to a final torque of 65 ft. Ibs. Install the oil pan. _ V6 and V8 Gasoline Engines

1980-1985 MODELS 1. Remove the engine oil pan. 2. Remove the oil pump and the rear main bearing cap. 3. Using a small pry bar, pry the oil seal from the rear main bearing cap. 4. Using a small hammer and a brass pin punch, drive the top half of the oil seal from the rear main bearing. Drive it out far enough, so it may be removed with a pair of pliers. 5. Using a non-abrasive cleaner, clean the rear main bearing cap and the crankshaft. 6. Fabricate an oil seal installation tool from 0.004 inch shim stock, shape the end to ‘2 inch long by ‘Yea inch wide.

1. Remove the transmission from the vehicle. 2. Using the notches provided in the rear seal retainer, pry out the seal using the proper tool.

s»Care should be taken when removing the seal so as not to nick the crankshaft sealing surface. 3. Before installation lubricate the new seal with clean engine oil. 4. Install the seal on tool J-3561 or equivalent. Thread the tool into the rear of the crankshaft. Tighten the screws snugly, this is to insure that the seal will be installed squarely over the crankshaft. Tighten the tool wing nut until it bottoms. 5. Remove the tool from the crankshaft. 6. Install the transmission. One Piece Seal Retainer and Gasket

1986 — 87 ENGINES

1. 2. 3. 4,

Remove Remove Remove Remove

the the the the

transmission from the vehicle. oil pan bolts. Lower the oil pan. retainer and seal assembly. gasket.

me»Whenever the retainer is removed a new retainer gasket and rear main seal must be installed.

7. Coat the new oil seal with engine oil; DO NOT coat the ends of the seal. 8. Position the fabricated tool between the crankshaft and the seal seat in the cylinder case. 9. Position the new half seal between the crankshaft and the top of the tool, so that the seal bead contacts the tip of the tool.

e*Make sure that the seal lip is positioned toward the front of the engine.

85773137

Fig. 191 Rear main seal removal notches, 1986-87 V6 and V8

ENGINE AND ENGINE REBUILDING

3-77

3. Measure the amount the seal was driven up on one side; add ‘6 inch, then cut this length from the old seal that was removed from the main bearing cap. Use a single-edge razor blade. Measure the amount the seal was driven up on the other side, add ‘6 inch and cut another length from the old seal. Use the man bearing cap as a holding fixture when Cutting the seal as illustrated. Carefully trim protruding seal. 4. Work these two pieces of seal up into the cylinder block on each side with two nailsets or small screwdrivers. Using the packing tool again, pack these pieces into the block, then trim them flush with a razor blade or hobby knife as shown. Do not scratch the bearing surface with the razor. 85773138

Fig. 192 Rear main seal installation, 1986-87 V6 and V8

e>|t may help to use a bit of oil on the short pieces of the rope seal when packing it into the block. 5. Apply Loctite® No. 496 sealer or equivalent to the rear main bearing cap and install the rope seal. Cut the ends of the seal flush with the cap. : 6. Check to see if the rear main cap with the new seal will seat properly on the block. Place a piece of Plastigage® on the rear main journal, install the cap and torque to 70 ft. Ibs. Remove the cap and check the Plastigage® against specifications. If out of specs, recheck the ends of the seal for fraying that may be preventing the cap from seating properly. 7. Make sure all traces of Plastigage® are removed from the crankshaft journal. Apply a thin film of sealer (GM part No. 1052357 or equivalent) to the bearing cap. Keep the sealant off of both the seal and bearing. 8. Just before assembly, apply a light coat of clean engineoil on the crankshaft surface that will contact the seal. 9. Install the bearing cap and torque the bolts to specifications. 10. Install the oil pump and oil pan.

Crankshaft and Main Bearings A. Rear of block 1. Seal retainer 2. Crankshaft

3. Gasket 4. Screw

CRANKSHAFT REMOVAL 85773139

» See Figure 194 Fig. 193 Rear main seal retainer installation, 1986-87 V6 and V8

5. Installation is the reverse of the removal procedure. Once the oil pan has been installed the new rear main oil seal can be installed.

8-350 and 8-379 Diesel The crankshaft need not be removed to replace the rear main bearing upper oil seal. The lower seal is installed in the bearing cap. 1. Drain the crankcase oil and remove the oil pan and rear main bearing cap. 2. Using a special main seal tool or a tool that can be made from a dowel (see illustration), drive the upper seal into its groove on each side until it is tightly packed. This is usually Ya-4/4 inch.

1. Drain the engine oil and remove the engine from the car. Mount the engine on a work stand in a suitable working area. Invert the engine, so the oil pan is facing up. 2. Remove the engine front (timing) cover. 3. Remove the timing chain and gears. 4. Remove the oil pan. 5. Remove the oil pump. 6. Stamp the cylinder number on the machined surfaces of the bolt bosses of the connecting rods and caps for identification when reinstalling. If the pistons are to be removed eventually from the connecting rod, mark the cylinder number on the pistons with silver paint or felt-tip pen for proper cylinder identification and cap-to-rod location. 7. Remove the connecting rod caps. Install lengths of rubber hose on each of the connecting rod bolts, to protect the crank journals when the crank is removed. 8. Mark the main bearing caps with a number punch or punch so that they can be reinstalled in their original positions. 9. Remove all main bearing caps.

ENGINE AND ENGINE REBUILDING

3-78

10. Note the position of the keyway in the crankshaft so it . can be installed in the same position. connecting each on bolt a between bands 11. Install rubber ~ rod and oil pan bolts that have been reinstalled in the block. This will keep the rods from banging on the block when the crank is removed. 12. Carefully lift the crankshaft out of the block. The rods will pivot to the center of the engine when the crank is removed.

MAIN BEARING INSPECTION AND REPLACEMENT The connecting rod big-end bearings and the crankshaft main bearings are shell-type inserts that do not utilize shims and cannot be adjusted. The bearings are available in various standard and undersizes; if main bearing clearance is found to be too sloppy, a new bearing (both upper and lower halves) is required. e»Factory undersized crankshafts are marked, sometimes with a 9 and/or a large spot of light green paint; the bearing caps also will have the paint on each side of the undersized journal. Generally, the lower half of the bearing shell (except No. 1 bearing) shows greater wear and fatigue. If the lower half only shows the effects of normal wear (no heavy scoring or discoloration), it can usually be assumed that the upper half is also in good shape; conversely, if the lower half is heavily worn or

damaged, both halves should be replaced. Never replace one bearing half without replacing the other.

CHECKING CLEARANCE Main bearing clearance can be checked both with the crankshaft in the car and with the engine out of the car. If the engine block is still in the car, the crankshaft should be supported both front and rear (by the damper and to remove clearance from the upper bearing.) Total clearance can then be measured between the lower bearing and journal. If the block has been removed from the car, and is inverted, the crank will rest on the upper bearings and the total clearance can be measured between the lower bearing and journal. Clearance is checked in the same manner as the connecting rod bearings, with Plastigage®. e>Crankshaft bearing caps and bearing shells should NEVER be filed flush with the cap-to-block mating surface to adjust for wear in the old bearings. Always install new bearings. 1. If the crankshaft has been removed, install it (block removed from car). If the block is still in the car, remove the oil pan and oil pump. Starting with the rear bearing cap, remove the cap and wipe all oil from the crank journal and bearing cap. 2. Place a strip of Plastigage® the full width of the bearing (parallel to the crankshaft), on the journal.

Do not rotate the crankshaft while the gauging material is between the bearing and the journal. 3. Install the bearing cap and evenly torque the cap bolts to specification. 4. Remove the bearing cap. The flattened Plastigage® will be sticking to either the bearing shell or the crank journal. 5. Use the graduated scale on the Plastigage® envelope to measure the material at its widest point.

elf the flattened Plastigage® tapers towards the middle or ends, there is a difference in clearance indicating the bearing or journal has a taper, low spot or other irregularity. If this is indicated, measure the crank journal with a micrometer.

ATA @ —] FRONTOF ENGINE oe . . . . . .

@

Rubber hose #41rod #3 rod Oil pan bolt Note overlap of adjacent rods Rubber bands 85773140

Fig. 194 Crankshaft removal showing hose lengths on rod bolts

6. If bearing clearance is within specifications, the bearing insert is in good shape. Replace the insert if the clearance is not within specifications. Always replace both upper and lower inserts as a unit. 7. Standard, 0.001 inch or 0.002 inch undersize bearings should produce the proper clearance. If these sizes still produce too sloppy a fit, the crankshaft must be reground for use with the next undersize bearing. Recheck all clearances after installing new bearings. 8. Replace the rest of the bearings in the same manner. After all bearings have been checked, rotate the crankshaft to make sure there is no excessive drag. When checking the No. 1 main bearing, loosen the accessory drive belts (engine in car) to prevent a tapered reading with the Plastigage®.

ENGINE AND ENGINE REBUILDING 3-79 Main Bearing » See Figures 195, 196, 197 and 198

REPLACEMENT Engine Out of Car 5°

1. Remove and inspect the crankshaft. 2. Remove the main bearings from the bearing saddles in the cylinder block and main bearing caps. 3. Coat the bearing surfaces of the new, correct size main bearings with clean engine oil and install them in the bearing saddles in the block and in the main bearing caps. 4. Install the crankshaft. See Crankshaft Installation.

} 85773141

Fig. 197 Home-made bearing roll-out pin

Engine in Car 1. With the oil pan, oil pump and spark plugs removed, remove the cap from the main bearing needing replacement and remove the bearing from the cap. 2. Make a bearing roll-out pin, using a bent cotter pin as shown in the illustration. Install the end of the pin in the oil hole in the crankshaft journal. 3. Rotate the crankshaft clockwise as viewed from the front of the engine. This will roll the upper bearing out of the block. 4. Lube the new upper bearing with clean engine oil and insert the plain (un-notched) end between the crankshaft and the indented or notched side of the block. Roll the bearing into

© 85773225

Fig. 198 With the bearing roll-out pin installed, rotate the crankshaft clockwise to push the upper bearing from the block place, making sure that the oil holes are aligned. Remove the roll pin from the oil hole. 5. Lube the new lower bearing and install the main bearing cap. Install the main bearing cap, making sure it is positioned in proper direction with the matchmarks in alignment. 6. Torque the main bearing cap bolts to specification. m>See Crankshaft Installation for thrust bearing alignment.

CRANKSHAFT END PLAY AND INSTALLATION » See Figure 199 85773223

Fig. 195 Remove the bearing cap from the main bearing that needs to be replaced

Fig. 196 Remove the bearing from the cap

When main bearing clearance has been checked, bearings examined and/or replaced, the crankshaft can be installed. Thoroughly clean the upper and lower bearing surfaces, and lube them with clean engine oil. Install the crankshaft and main bearing caps. Dip all main bearing cap bolts in clean oil, and torque all main bearing caps, excluding the thrust bearing cap, to specifications (see the Crankshaft and Connecting Rod chart in this Section to determine which bearing is the thrust bearing). Tighten the thrust bearing, pry the crankshaft the extent of its axial travel several times, holding the last movement toward the front of the engine. Add thrust washers if required for proper alignment. Torque the thrust bearing cap to specifications. To check crankshaft end-play, pry the crankshaft to the extreme rear of its axial travel, then to the extreme front of its travel. Using a feeler gauge, measure the end-play at the front of the rear main bearing. End-play may also be measured at

err

3.80 ENGINE AND ENGINE REBUILDING the thrust bearing. Install a new rear main bearing oil seal in the cylinder block and main bearing cap. Continue to reassemble the engine.

Flywheel and Ring Gear

;

REMOVAL & INSTALLATION The ring gear is an integral part of the flywheel and is not replaceable. 1. Remove the transmission. 2. Remove the six bolts attaching the flywheel to the crankshaft flange. Remove the flywheel. 3. Inspect the flywheel for cracks, and inspect the ring gear for burrs or worn teeth. Replace the flywheel if any damage is apparent. Remove burrs with a mill file.

85773143

Fig. 199 Measuring crankshaft end-play at the front of the rear main bearing 4. Install the flywheel. The flywheel will only attach to the crankshaft in one position, as the bolt holes are unevenly spaced. Install the bolts and torque to specification.

EXHAUST SYSTEM » See Figures 200 and 201

2k CAUTION Never work on your truck’s exhaust when it has just been used. The exhaust system reaches extremely high temperatures and can cause severe burns. Always allow the truck to cool completely before attempting any exhaust repair. The exhaust system is suspended by hangers attached to the frame members. Annoying rattles and noise vibrations in the Exhaust System are usually caused by misalignment of parts. When aligning the system, leave all bolts or nuts loose until all parts are properly aligned, then tighten, working from front to rear. When replacing a muffler, the tailpipe(s) should also be replaced. Sealer such as 1051249, or equivalent, should be used at all clamped joint connections.

When jacking or lifting vehicle from frame side rails, be certain lift pads do not contact catalytic converter as damage to converter will result.

Catalytic Converter The catalytic converter is an emission control device added to a gasoline engine light duty emission exhaust system to reduce hydrocarbon and carbon monoxide pollutants from the exhaust gas stream. The catalyst in the converter is not serviceable. THE CATALYTIC CONVERTER REQUIRES THE USE OF UNLEADED FUEL ONLY.

8

6

Fig. 200 The crossover pipe runs from the manifolds to the catalytic converter, the intermediate pipe connects the converter to the muffler assembly, then the exhaust is taken over the axle and vented to the rear of the vehicle

Periodic maintenance of the exhaust system is not required; however, if the vehicle is raised for other service; it is advisa-

ble to check the general condition of the catalytic converter, pipes and muffler(s).

ENGINE AND ENGINE REBUILDING

3-81

12 Nem

(100 Ib. in.)

85773146

Fig. 201 Catalytic converter installation

System Components REMOVAL Manifolds

The exhaust manifold studs have to be heated, in most cases, before they can be removed. If the studs are badly rusted, there is a large possibility that they will break off inside the manifold. If this happens, the studs will have to be drilled out of the manifold, and the manifold retapped. Due to the cost of the equipment necessary to perform this procedure, it is recommended that it be done by a qualified mechanic. Exhaust and Y-Pipe Two studs hold the exhaust pipe to the manifold on four and in-line 6 cylinder engines. Four studs hold the Y-pipe on V6 and V8 models. A good quality lubricant, such as Liquid Wrench, should be applied to the studs before attempting to remove the nuts. Use a wire brush to remove some of the rust on the studs, this will make removing the nuts earlier. If the nuts are frozen to the studs, they will have to be heated to be removed. Before applying heat to the studs, make sure that you have removed the lubricant completely from the studs and nuts, as some lubricants are highly flammable. If the studs appear to be badly worn, and will probably break if the necessary force to free the nuts is applied, refer servicing to a qualified mechanic.

Catalytic Converter The catalytic converter is connected to the exhaust or Y-pipe and the muffler by a muffler clamp. After removing the clamps, it may be necessary to use a hammer and chisel to separate the converter from the exhaust or Y-pipe and the muffler. Be careful not to damage any parts of the exhaust system that do not need to be replaced. Replace all clamps, nuts, bolts and straps. You do not want your new exhaust system to fall on the ground due to a worn clamp. Muffler

The muffler is attached to the catalytic converter by a muffler clamp, to the frame by two muffler hangers and to the tail pipe by a muffler clamp. After removing the clamps and hangers, it may be necessary to use a hammer and chisel to separate the muffler from the tail pipe. Tail Pipe The tail pipe is removed by loosening the nuts on the hanger that secure the pipe to the frame.

INSTALLATION Exhaust System Sealer is to be applied to all slip joints before assembly. When installing exhaust parts, make sure there is sufficient clearance between the hot exhaust parts and pipes and hoses that would be adversely affected by excessive heat.

~ 3.82 ENGINE AND ENGINE REBUIEDING — Check complete exhaust system and nearby body areas and trunk lid for broken, damaged, missing, or mispositioned parts, open seams, holes, loose connections, or other deterioration which could permit exhaust fumes to seep into the passenger compartment. Any damaged areas must be corrected immediately. To help insure continued integrity, when replacing the muffler, resonator or pipes rearward of the muffler due to wear out, all parts. rearward and including the muffler should be replaced.

When aligning the system, leave all bolts or nuts loose until “all parts are properly aligned, then tighten, working from front to rear.

If any mispositioning, incorrect assembly, or failure of

components in the area of the brake system pipes, hoses, or cylinders is observed, be sure to check for any brake damage that may have resulted from such a condition and “correct as required. Make sure that exhaust system components have adequate clearance from the floor pan to avoid possible overheating of the floor pan and possible damage to the passenger compartment carpets. When jacking or lifting vehicle from frame side rails, be certain lift pads do not contact catalytic converter as damage to converter will result.

we

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ENGINE AND ENGINE REBUILDING 3-83 Ae

IE

SPRITE LE

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BESO

SES PO

SN

LIL BI ES SD SEES

ESE ST OEE EIS 5 TES AGES STIPE ERE OSTST

SE

SES TES

TSN

SE

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DEI ED,

TORQUE SPECIFICATIONS Component

Auxillary Cooling Fan All Engines Camshaft Sprocket Bolts 4.3L Engine 5.0L and 5.7L Gas Engine 6.2L Diesel Engine 7.4L Engine 5.7L Diesel Engine Camshaft Thrust Plate 4.1L and 4.8L Engine 4.3L Engine 6.2L Diesel Engine Connecting Rod Cap Nuts 4.1L, 4.3L, 4.8L, 5.0 and 5.7L Gas Engine 6.2L Diesel Engine 7.4L Engine 5.7L Diesel Engine Flywheel Housing Bolts 4.1L, 4.3L, 4.8L, 5.0 and 5.7L Gas

U.S.

Metric

53 ft. Ibs.

72 Nm

17 18 75 20 65

23 24 100 26 88

ft. ft. ft. ft. ft.

Ibs. Ibs. Ibs. Ibs. Ibs.

80 ft. Ibs. 105 ft. Ibs. 75 ft. Ibs.

90 Nm 119 Nm 100 Nm

.

&

45 ft. Ibs. 48 ft. Ibs. 48 ft. Ibs.

60 Nm 66 Nm 66 Nm

42 ft. Ibs.

57 Nm

Engine

Sarita lDSaaaee

6.2L and 7.4L Gas Engine

30 ft. Ibs.

Z

‘

44 Nm

4

40 Nm

Front Cover to Block Bolts

i

4.1L and 4.8L Engine

80 inch Ibs.

4.3L, 5.0L and 5.7L Gas Engine

100 inch Ibs.

6.2L Diesel Engine

33 ft. Ibs.

7.4L Engine 5.7L Diesel Engine

96 inch Ibs. 80 inch Ibs.

Front Cover Bolts to Oil Pan 4.1 and 4.8L Gas Engine 7.4L Engine

Hydraulic Lifter Restrictor Retainer 4.3L Engine

Hydraulic Lifter Guide Plate 6.2L Diesel Engine Main Bearing Cap Bolts 4.1L and 4.8L Engine 4.3L Engine 5.0L and 5.7L Gas Engine Outer Bolts 2, 3, and 4 5.0L and 5.7L Gas Engines Inner bolts 6.2L Diesel Engine Inner Bolts 6.2L Diesel Engine Outer Bolts 7.4L Engine 5.7L Diesel Engine

Nm Nm Nm Nm Nm

ee 3

ae

11.38 Nm

45 Nm 10.8 Nm 9.0 Nm

_

5.1 Nm

70 inch Ibs.

ae

ae

:

45 inch Ibs.

d 9.0 Nm

7.9 Nm

Se

Fi

145 inch Ibs.

16 Nm

18 ft. Ibs.

65 ft. Ibs. 75 ft. Ibs. 70 ft. Ibs.

95 Nm-#*

80 65 100 110 120

110 90 135 150 163

ft. Ibs. ft. Ibs. ft. Ibs. ft. Ibs. ft. Ibs.

ee

Nm Nm Nm Nm Nm

Se

8577c120

ENGINE AND ENGINE REBUILDING

3.84

TORQUE

|

SPECIFICATIONS

Component a

Oil Pan

80 inch Ibs.

4.1L 4.3L, 4.3L, 6.2L 6.2L 7.4L 5.7L

165 inch Ibs. 200 inch Ibs. 11 inch Ibs. 17 ft. Ibs. 84 inch Ibs. 160 inch Ibs. 10 ft. Ibs.

4.1L and 4.8L Engine 1/4 bolts

;

and 4.8L Engine 5/16 bolts 5.0L and 5.7L Engine Nuts 5.0L and 5.7L Engine Bolts Diesel Engine Rear Two Bolts Diesel Engine All Other Bolts Engine Diesel Engine

Oil Pump

70 inch Ibs.

5.0L and 5.7L Engine

80 inch Ibs.

5.7L Diesel Engine

8 ft. Ibs.

Pump Pickup Tube

4.8L Engine

Arm Cover and 4.8L Engine Engine and 5.7L Engine Studs and 5.7L Carbureted Engine

25 ft. Ibs. 38 11 15 65

;

Starter All Engines Torsional Damper Bolt 4.1L and 4.8L Engine 4.3L, 5.0L and 5.7L Engine 6.2L Diesel Engine 7.4L Engine 5.7L Diesel Engine Water Outlet

_

as

4.3L, 5.0L and 5.7L Engine 6.2L Diesel Engine

7.4L Engine

Water Pump 4.1L and 4.8L Engine 4.3L, 5.0L, 5.7L and 7.4L Engine 6.2L Diesel Engine 5.7L Diesel Engine

inch Ibs. inch Ibs.

inch Ibs. inch Ibs.

11 inch Ibs.

Diesel Engine Rear Engine Diesel Engine Shaft Bolts Diesel Engine Arm Pivot Bolt Diesel Engine

4.1L and 4.8L Engine

90 Nm 13 Nm 42 Nm 47 Nm

‘

7.9 Nm

9.0 in 11

Nm

34 Nm

:

5.0L and 5.7L TBI Engine Bolts

6.2L 7.4L 5.7L Rocker 6.2L ' Rocker 5.7L

‘

115 inch Ibs. 31 ft. Ibs. 35 ft. Ibs.

Oil Pump Cover 4.8L Engine

Rocker 4.1L 4.3L 5.0L 5.0L

9.0 Nm 18.6 Nm 22 Nm 1.2 Nm 23 Nm 10 Nm 18.1 Nm 14 Nm

65 ft. Ibs.

4.3L, 5.0L, 5.7L and 7.4L Engine 4.1L and 4.8L Engine 6.2L Diesel Engine 5.7L Diesel Engine

Oil

Metric

U.S.

h t

:

4.3 1.2 1.7 7.3

Nm Nm

Nm Nm

1.2 Nm

26 ft. Ibs. 115 inch Ibs. 65 inch Ibs.

35 Nm 13 Nm 7.3 Nm

40 ft. Ibs.

55 Nm

28 ft. Ibs.

38 Nm

28 ft. Ibs.

38 Nm

50 ft. Ibs. 70 ft. Ibs. 200 ft. Ibs. 85 ft. Ibs. 200-310 ft. Ibs.

70 Nm 95 Nm 270 Nm 115 Nm 270-420 Nm

28 ft. Ibs.

38 Nm

21 ft. Ibs. 31 ft. Ibs.

30 ft. Ibs.

15 30 32 13

ft. ft. ft. ft.

Ibs. Ibs. Ibs. Ibs.

28 Nm 42 Nm

40 Nm

20 40 42 18

Nm Nm Nm Nm 8577c121

DIAGNOSTIC TROUBLE CODES — DIESEL ENGINE 4-30 DIAGNOSTIC TROUBLE CODES — GASOLINE ENGINES 4-24 DIESEL ENGINE EMISSIONS CONTROLS CRANKCASE VENTILATION 4-25 DIESEL ELECTRONIC CONTROL SYSTEM CALIFORNIA ONLY 4-29 EXHAUST GAS RECIRCULATION (EGR) 4-25 VACUUM PUMP. 4-29 GASOLINE ENGINE EMISSION CONTROLS AIR INJECTOR REACTOR (A.I.R.) 4-3 CATALYTIC CONVERTER 4-18 COMPUTER COMMAND CONTROL (CCC) SYSTEM (CALIFORNIA OR FUEL INJECTED ENGINES ONLY) 4-22 EARLY FUEL EVAPORATION 4-14 ELECTRONIC SPARK CONTROL (ESC) SYSTEM (CALIFORNIA OR FUEL INJECTED ONLY) 4-21 ELECTRONIC SPARK TIMING (EST) SYSTEM (CALIFORNIA OR FUEL INJECTED ONLY) 4-21 EVAPORATIVE EMISSION CONTROL SYSTEM 4-11 EXHAUST GAS RECIRCULATION 4-19 OXYGEN SENSOR 4-18 POSITIVE CRANKCASE VENTILATION 4-2 PULSE AIR INJECTION 4-7 THERMOSTATIC AIR CLEANER 4-7 THROTTLE RETURN CONTROL 4-15 TRAPPED VACUUM SPARK 4-19 VACUUM DIAGRAMS 4-30

EMISSION CONTROLS DIAGNOSTIC TROUBLE CODES — DIESEL ENGINE DIAGNOSTIC. TROUBLE CODES — GASOLINE ENGINES DIESEL ENGINE EMISSIONS CONTROLS. GASOLINE ENGINE EMISSION CONTROLS VACUUM DIAGRAMS:

4-30 4-24 4-25 ~ 4-2 4-30

4-2

EMISSION CONTROLS

ee

a

GASOLINE ENGINE EMISSION CONTROLS » See Figures 1 and 2 The emission control devices required in Chevrolet and GMC pick-ups are determined by weight classification. All trucks under 8,600 Ibs. GVW are light duty emission models and use the same controls as can be found on cars. All four wheel drive vehicles and trucks over 8,600 lbs. GVW are considered . heavy duty models and use fewer emission controls. With emission level maintenance standards getting stricter on state and Federal levels, proper testing and service of each system becomes more important. Much confusion results from the variety and combinations of systems used in any year. Factors such as engine, build date, and geographic location are just some variables that determine what emission controls are installed on the truck. Not all of the systems described are in all vehicles, it’s always best to consult the truck’s vehicle emission label to determine what systems are installed on the truck your working on. The label also includes a vacuum schematic of the system on the truck which is very helpful when servicing the emission systems. If the emission label is missing or illegible a new one can be ordered at the dealer, but call the dealer ahead of time to find out what information is required to order the correct label. One very important point to keep in mind when working on the emission system is to tag or identify ALL hoses and wires that are removed during service. Reinstalling wires and hoses incorrectly can cause disable emission systems, leading to excessive exhaust emissions and poor driveability. Attempting to reconnect the various vacuum hoses without a reference point can be extremely difficult.

Positive Crankcase Ventilation OPERATION » See Figures 3, 4, 5, 6 and 7 The Positive Crankcase Ventilation (PCV) system is used to evacuate the crankcase of vapors. Outside air is routed through a breather in the air cleaner to the crankcase where it mixes with the blow-by gases and is passed through the PCV valve. It is then routed into the intake manifold. The PCV valve meters the air flow rate which varies under engine operation

85774106

Fig. 2 One look at this rat’s nest of wires and hoses should convince you of the need to tag before disconnecting depending on manifold vacuum. In order to maintain idle quality, the PCV valve limits the air flow when intake manifold vacuum is high. If abnormal operating conditions occur, the system will allow excessive blow-by gases to back flow through the crankcase vent tube into the air cleaner. These blow-by gases will then be burned by normal combustion. A plugged PCV valve or hose may cause rough idle, stalling or slow idle speed, oil leaks, oil in the air cleaner or sludge in the engine. A leaking PCV valve or hose could cause rough idle, stalling or high idle speed. Other than checking and replacing the PCV valve, breather and associated hoses, there is no service required. Engine operating conditions that would direct suspicion to the PCV

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i 85774088

Fig. 1 The vehicle emission label, found in the engine compartment, contains engine tune-up and emission control system information

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FRESH-AIR

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§=MIXTURE OF FRESH-AIR AND BLOW-| BY GAS

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BLOW-BY

85774001

Fig. 3 PCV System

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GASES }

CRANKCASE BLOW-BY GASES

EMISSION CONTROLS

POSITIVE

METERED

VENTILATION (STD)

NON. VENTED | Be. (? CaP

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4-3

ORIFICE

57 =

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VENTILATION 7 A\\ 85774002

Fig. 4 Closed and positive PCV systems, 6-cylinder shown

Fig. 5 To remove the breather from the air cleaner you must first disconnect the valve cover hose

system are rough idle, oil present in the air cleaner, oil leaks and excessive oil sludging or dilution. If any of the above conditions exist, remove the PCV valve and shake it. A clicking sound indicates that the valve is free. If no clicking sound is heard, replace the valve. Inspect the PCV breather in the air cleaner. Replace the breather if it is so dirty that it will not allow gases to pass through. Check all the PCV hoses for condition and tight connections. Replace any hoses that have deteriorated.

REMOVAL, TESTING & INSTALLATION 1. Remove PCV valve from the rocker arm cover. Do not disconnect the vacuum hose from the valve. 2. Start the engine and allow it to reach normal operating temperature. Continue to run the engine at idle. 3. Place your thumb over the end of the valve to check if vacuum is present at the valve. If vacuum is not present, check for plugged hoses or blockage at the manifold port or a faulty PCV valve. Replace as necessary.

Air Injector Reactor. (A.1.R.) » See Figures 8, 9, 10, 11, 12 and 13

OPERATION The AIR system injects compressed air into the exhaust system, near the exhaust valves to aid in the continued burn-

"85774090

Fig. 6 Once the hose is disconnected, remove the Cclip and the breather can be pulled from the air cleaner assembly

4-4

EMISSION CONTROLS AIR PUMP

1G GZS

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NY

DISTRIBUTOR:

TOEACH CYLINDER

.

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} DISTRIBUTOR TO EACH CYLINDER KEY TOAI.R, SYSTEM

PISTON EXHAUST

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PCV VALVE

85774003

STROKE AFTER COMBUSTION

Coo FILTEREDAIR HYDROCARBONS AND

°° CARBON MONOXIDE wah TREATED EXHAUST

(TO ATMOSPHERE THROUGH EXHAUST PIPE)

85774004

Fig. 7 V8 PCV valve location ing of exhaust gases. The system reduces the carbon monoxide (CO) and hydrocarbon levels in the exhaust gas that would normally be released into the atmosphere by increasing the oxygen content in the exhaust. Increasing the oxygen content in the exhaust gas enhances burning very much like increasing the draft or flow in a fireplace. To do this the system employs an air injection pump, a diverter valve, a check valve, and a system of hoses and tubes necessary to carry the compressed air from the pump to the exhaust manifolds. The diverter valve is used to bypass air away from the exhaust system when the engine is decelerating or operating at continuous high speeds. If the system was not able to divert air during deceleration, backfiring in the manifold would occur. The diverter valve is a vacuum operated valve on early models and in some later models particularly on California vehicles, an electric solenoid valve was used. The vacuum operated diverted valves have a vacuum line connected to the intake manifold or carburetor, as engine speed decreases intake manifold vacuum increases. The increased vacuum causes the valve to open and divert air away from the exhaust manifold. On the electrically operated valves the Engine Control Module (ECM) or a contro! module controls the valve operation by applying ground to the air diver solenoid terminal ‘B’. Battery voltage is applied to the solenoid ‘A’ terminal whenever the ignition is on. When the module applies ground, the solenoid energizes which causes the valve to direct air to the exhaust ports. The module operates the valve based on coolant temperature, engine speed and manifold vacuum. When the ‘CHECK ENGINE’ light is on the module will turn the solenoid off which will result in air being diverted to the air cleaner. Check valves are also employed in the system to prevent the introduction of exhaust gases into the AIR systems plumbing and components.

TESTING Check Valve

To test the check valve, disconnect the hose at the diverter valve. Blow into the hose and then draw air from the hose. Be careful not to inhale any foreign substances during this procedure. Air should flow into the engine only. Diverter Valve

1. Pull off the vacuum line to the top of the valve with the engine running. There should be vacuum in the line. Install the

Fig. 8 AIR system operation

85774005

Fig. 9 In-line six air pump mounting vacuum line and inspect. No air should be escaping with the engine running at a steady idle. 2. Open and quickly close the throttle. A blast of air should come out of the valve muffler or air cleaner for at least one second. 3. If the truck is equipped with a electric diverter valve go to the next Step. If not equipped with the electric type go to Step 6. 4. Disconnect the harness connector from the solenoid and then turn the ignition on. Connect a voltmeter or test light between terminal A on the harness connector and ground. a. If 10 volts or greater is measured or the test light lights, the solenoid is getting power. b. If less than 10 volts is measured or the test light does not light, the solenoid is not getting power due to an open or short to ground in the wiring. 5. Measure the resistance across the solenoid by connecting an ohmmeter between the two terminals on the solenoid.

Make sure that the solenoid is disconnected or a false reading may occur. The resistance of the solenoid should equal about 20 ohms. a. If the resistance is less than 20 ohms, the solenoid is shorted. Replace the solenoid and the Engine Control Module (ECM), as required. b. If the resistance is more than 20 ohms, the solenoid is open. Replace the solenoid. 6. If the valve must be replaced, use a new gasket at the valve mounting on the pump and torque the bolts to 85 inch lbs. (9.5 Nm).

EMISSION CONTROLS

4-5

AIR PUMP

VACUUM FITTING

VACUUM DIFFERENTIAL VALV'

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VACUUM -

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DELAY VALVE

BY PASS VALVE

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85774006

Fig. 10 Air pump system, V8 Air Pump

Disconnect the hose from the diverter valve. Start the engine and accelerate it to about 1,500 rpm. The airflows should increase as the engine is accelerated. If no airflow is noted or it remains constant, check the following:

1. Inspect the drive belt tension and correct, if necessary. 2. Listen for a leaking pressure relief valve. If it is defective, replace the relief/diverter valve assembly. 3. Inspect for foreign matter in the pump filter openings. If the pump is defective or excessively noisy, it must be replaced. 85774007

SERVICE The AIR system's effectiveness depends on correct engine idle speed and ignition timing. These settings should be strictly wae

AIR MANAGEMENT VALVE

GASKET

adhered to and checked frequently. All hoses and fittings

should be inspected for condition and tightness of connections. Check the drive belt for wear and tension every 12 months or 12,000 miles. If, after completion of a tune-up and/or individual

85774008

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Fig. 12 AIR diverter valve, 1980 and later vehicles

inspection of components, a malfunction still exists, the vehicle should be serviced by qualified mechanics. The AIR system is not completely noiseless. Under normal conditions, noise rises in pitch as engine speed increases. To determine if excessive noise is the fault of the AIR system, operate the engine with the pump drive belt removed. If the noise does not exist with the belt removed: 1. Check for a seized pump. 2. Check hoses, tubes and connections for leaks or kinks.

4-6

EMISSION CONTROLS

CE

AIR CONVERTER

se

CONVERTER AND CHECK PIPE VALVE CLAMP

HOSE

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AIR MANAGEMENT VALVE

85774009

Fig. 13 Check valve and hoses — 1981 and later air management system

3. Check the diverter valve. 4. Check the pump for proper mounting.

Do not oil AIR pump. If no irregularities exist and the AIR pump noise is still excessive, replace the pump.

REMOVAL & INSTALLATION Air Pump

"85774091

Fig. 14 When removing the pump, first disconnect the air hose from the rea of the housing

» See Figure 14

WARNING Do not pry on the pump housing or clamp the pump in a vise: the housing is soft and may become distorted. 1. Disconnect the air hoses at the pump. 2. Hold the pump pulley from turning and loosen the pulley bolts. 3. Loosen the pump mounting bolt and adjustment bracket bolt. Remove the drive belt. 4, Remove the mounting bolts, and then remove the pump.

5. Install the pump using a reverse of the removal procedure. Check Valve

1. Release the clamp and disconnect the air hoses from the valve. 2. Unscrew the check valve from the air injection pipe. 3. Installation is in the reverse order of removal. Pump Filter 1. Remove the drive belt and pump pulley.

EMISSION CONTROLS SE

PSE

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PSR

SN

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: 2. Using needle nose pliers, pull the fan from the pump ub.

+ WARNING Use care to prevent any dirt or fragments from entering the air intake hole. DO NOT insert a screwdriver between the pump and the filter, and do not attempt to remove the

metal hub. It is seldom possible to remove the filter without destroying it. 3. To install a new filter, draw it on with the pulley and pulley bolts. Do not hammer or press the filter on the pump. 4. Draw the filter down evenly by torquing the bolts alternately. Make sure the outer edge of the filter slips into the housing. A slight amount of interference with the housing bore is normal. =The new filter may squeal initially until the sealing lip on the pump outer diameter has worn in.

Diverter (Anti-afterburn) Valve 1. Turn the ignition off and disconnect the negative battery cable if vehicle is equipped with the electric solenoid valve. 2. Detach the vacuum sensing line from the valve. Disconnect the wire harness connector if the valve is the electric type.

3. Remove the other hose(s) from the valve. 4. Unfasten the diverter valve from the elbow or the pump body. 5. Installation is performed in the reverse order of removal. Always use a new gasket. Tighten the valve securing bolts to 85 inch Ibs. (9.5 Nm).

Pulse Air Injection » See Figure 15

OPERATION The PAIR system is used on some 1980 and later 250 6-cylinder engines. The system utilizes exhaust system pulses to siphon fresh air into the exhaust manifold. The injected air supports continued combustion of the hot exhaust gases in the exhaust manifold, reducing exhaust emissions. Air is drawn into the PAIR plenums through a hose connected to the air cleaner case. There are two plenums, mounted on the rocker arm cover. The air passes through a check valve (there are four check valves — two at each plenum), then through a manifold pipe to the exhaust manifold. All manifold pipes are the same length, to prevent uneven puisation. The check valves open during pulses of negative exhaust back pressure, admitting air into the manifold pipe and the exhaust manifold. During pulses of positive exhaust back pressure, the check valves close, preventing backfiring into the plenums and air cleaner.

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4-7 ATS

TESTING 1. Visually check all system valves, pipes, hoses and grommets for any leaks or cracks. Repair or replace components, as necessary. 2. To check the operation of the pulse air valves, connect a handheld vacuum pump at the grommet end of the valve. 3. Apply a vacuum of 5 kPa (17 in. Hg) to the valve. Observe the gauge for an allowable drop in vacuum of 1.7 kPa (6 in. Hg) in two seconds. If vacuum loss is greater than specified than replace valve or hose.

REMOVAL & INSTALLATION 1. Remove the air cleaner. Disconnect the rubber hose from the plenum connecting pipe. 2. Disconnect the four manifold pipes at the exhaust manifold. Remove the check valves from the plenum grommets. 3. Unbolt the check valve from the manifold pipe, if necessary. 4. To install, assemble the check valves to the pipes before the pipes are installed on the exhaust manifold. 5. Install the manifold pipe fillings to the exhaust manifold, but tighten the fittings only finger tight. 6. Use a 1 in. open end wrench, or something similar, as a

lever to align the check valve on the A pipe assemblies (see the illustration) with the plenum grommet. Use the palm of your hand to press the check valve into the grommet. A rubber lubricant can be used to ease assembly. 7. Repeat this operation on the B pipe assembly. 8. After all the check valves have been installed in the rubber grommets, tighten the manifold pipe-to-exhaust manifold fittings to 28 ft. lbs. Connect the rubber hose to the plenum pipe and install the air cleaner.

Thermostatic Air Cleaner The thermostatic air cleaner (Thermac) is on all gasoline engines. This system uses a damper assembly in the air cleaner inlet, controlled by a vacuum motor to mix preheated and cold air entering the air cleaner. This is necessary to maintain a controlled air temperature into the carburetor. The vacuum motor is controlled by a temperature sensor in the air cleaner. The preheating of the air cleaner inlet air allows leaner carburetor and choke settings, which result in lower emissions, while maintaining good driveability.

TESTING 1. Either start with a cold engine or remove the air cleaner from the engine and allow to cool for at least 30 min. While cooling the air cleaner, leave the engine compartment hood open. 2. Tape a thermometer inside of the air cleaner so that it is near the temperature sensor unit. Install the air cleaner on the engine but do not fasten its securing nut.

4-8

EMISSION CONTROLS

PLENUM PIPE PLENUM

!

Ss

AIR CLEANER

wv GROMMETS

| Due to the position of the air cleaner on some trucks, a

mirror may be necessary when observing the position of the air door.

4. Operate the throttle lever rapidly to ‘/2-%4 of its opening and release it. The air door should open to allow outside air to enter and then close again. 5. Allow the engine to warm up to normal temperature. Watch the door. When it opens to the outside air, remove the cover from the air cleaner. The temperature should be over 90°F and no more than 130°F; 115°F is about normal. If the door does not work within these temperature ranges, or fails to

2. Remove the hose which runs from the sensor to the vacuum motor. Run a hose directly from the manifold vacuum source to the vacuum motor. 3. If the motor closes the air door, it is functioning properly and the temperature sensor is defective. 4. If the motor does not close the door and no binding is present in its operation, the vacuum motor is defective and must be replaced. elf an alternate vacuum source is applied to the motor, insert a vacuum gauge in the line by using a T-fitting. Apply at least 9 in. Hg of vacuum in order to operate the motor.

REMOVAL & INSTALLATION

work at all, check for linkage or door binding. If binding is not present and the air door is not working,

proceed with the vacuum tests, given below. If these indicate

Air Cleaner Assembly

no faults in the vacuum motor and the door is not working, the

» See Figures 16, 17, 18 and 19

temperature sensor is defective and must be replaced. Vacuum Motor Test

Be sure that the vacuum hose which runs between the temperature switch and the vacuum motor is not pinched by the retaining clip under the air cleaner. This could prevent the air door from closing.

1. Check all of the vacuum lines and fittings for leaks. Correct any leaks. If none are found, proceed with the test.

1. Loosen the wing nut and remove the air cleaner cover. 2. As applicable, disconnect the snorkel tube and air hoses from the air cleaner housing. 3. Lift up slightly on the end of the housing and disconnect the heat stove from either the exhaust manifold riser or from the bottom of the air cleaner snorkel. 4. Remove the air cleaner housing assembly from the vehicle. To install: 5. Install the air cleaner housing and connect the heat

stove.

EMISSION CONTROLS

4-9

85774096 85774093

Fig. 16 Make sure all air hoses are disconnected from the air cleaner housing

Fig. 18 Once all hoses and tubes have been disconnected, the air cleaner housing may be removed from the engine 6. Connect the snorkel tube and hoses to the air cleaner housing, as applicable. 7. Make sure the air cleaner is properly seated in the housing, then install the cover and tighten the wing nut.

85774095

Fig. 17 If access is easier, the heat stove may be disconnected from the air cleaner snorkel tube

4-10

EMISSION CONTROLS

74097

Fig. 19 Upon installation, make sure the heat stove is firmly seated on the exhaust manifold riser

85774098

Fig. 20 The vacuum diaphragm motor is located on the air cleaner snorkel tube

Vacuum Diaphragm Motor

» See Figures 20, 21 and 22 1. Remove the air cleaner. 2. Disconnect the vacuum hose from the motor. 3. Drill out the two spot welds with a ‘/e in. drill bit, then enlarge the hole as required to remove the retaining strap. Be careful not to damage the snorkel tube. Remove the retaining strap. 4. Lift up motor, cocking it to one side to unhook the motor

linkage at the control damper assembly. To install 5. Drill a 2.8mm (“es in.) hole in the snorkel tube at center of vacuum motor retaining strap. 6. Reattach the vacuum motor linkage into the control dampener. 7. Reattach the vacuum hose to the vacuum motor. 8. Reinstall the air cleaner.

Temperature Sensor » See Figures 23, 24, 25, 26 and 27 1. Remove the air cleaner. 2. Disconnect the vacuum hoses at the temperature sensor. 3. Pry up tabs on temperature sensor retaining clip. Remove clip and temperature sensor from the air cleaner. Note the position of temperature sensor before removing. To install 4. Install the temperature sensor in the same position as when removed. 5. Install retaining clip tabs into position. 6. Reconnect the vacuum hoses to the temperature sensor.

85774099

Fig. 21 The vacuum hose may be pulled from the motor nipple by hand

EMISSION CONTROLS

4-11

DRILL 7/64” HOLE IN CENTER POSITION OF STRAP

SPOTWELDS VACUUM : DIAPHRAGM,

RETAINING STRAP

INSTALL REPLACEMENT SENSOR ASSM. IN SAME POSITION AS ORIGINAL ASSM 85774082

Fig. 22 Vacuum diaphragm motor and air sensor removal

85774101

Fig. 24 Invert the housing and disconnect the vacuum hoses from the sensor

85774100

Fig. 23 The temperature sensor is mounted inside the air cleaner housing 7. Reinstali the air cleaner.

Evaporative Emission Control System GENERAL INFORMATION » See Figures 28 and 29 The Evaporative Emission Control System (EECS) is designed to prevent fuel tank vapors from being emitted into the atmosphere. The primary component in the system is the charcoal canister. The canister absorbs and stores gasoline vapors from the carburetor fuel bowl and the fuel tank for burning at a later time. On vehicles equipped with an auxiliary fuel tank, an

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i

85774102

Fig. 25 Release the tabs on the retaining clip and push down on the sensor nipples to free the sensor

4-12

EMISSION CONTROLS

:

pce

;

Fig. 26 Remove the retaining clip from the sensor and the housing

additional canister is installed to increase the vapor collection capacity. When engine coolant temperature reaches 49°C (120°F) and the engine is off idle, the system will allow the vapors to be purged into the intake manifold and burned by the engine. Three valves are used in the system; the cannister purge control valve which prevents vapors from escaping from the cannister when the system is not being purged, the vapor vent control valve which prevents venting of the fuel bowl during engine operation and the Thermostatic Vacuum Switch (TVS) which prevents purging before the engine warms. The purging cycle is controlled by the Thermostatic Vacuum Switch (TVS), which is installed in the coolant passage opens and closes depending on the temperature of the coolant. When engine operating temperature is below 115°F (46°C) the thermostatic vacuum switch is open and prevents vacuum from being applied to the cannister purge control valve. When coolant temperature reaches 49°C (120°F) the thermostatic vacuum switch closes to allow vacuum to be applied to the canister purge control valve. The applied vacuum lifts the canister purge valve diaphragm to open the valve and pull the collected fuel vapors into the intake. A vent located in the fuel tank allows fuel vapors to flow to the charcoal canister. A tank pressure control valve, used on high altitude applications, prevents canister purge when the engine is not running. The fuel tank cap does not normally vent to the atmosphere but is designed to provide both vacuum and pressure relief.

Poor engine idle, stalling and poor driveability can be caused

by a damaged canister or split, damaged or improperly connected hoses. Evidence of fuel loss or fuel vapor odor can be caused by a liquid fuel leak; a cracked or damaged vapor canister; disconnected, misrouted, kinked or damaged vapor pipe or canister hoses; or a damaged air cleaner or improperly seated air cleaner gasket.

:

California Models

On California models equipped with the Computer Command System the thermostatic vacuum switch is replaced with a electric solenoid valve that is controlled by the Engine Control Module (ECM). The Engine Control Module monitors coolant temperature, vehicle speed, and throttle position and then determines when to turn on the purge solenoid. The Engine Control Module (ECM) operates the valve by applying a ground to the solenoid.

TESTING Canister Purge Control Valve

85774104

Fig. 27 Withdraw the sensor from the inside of the

housing assembly

1. Connect a short length of hose to the vapor purge port on the canister purge valve and attempt to blow through the valve. Little or no air should pass through the valve. If air does pass through the valve, replace the canister. 2. Connect a hand vacuum pump to the purge valve vacuum port on the canister purge valve. Apply 51 kPa (15 in.

Fig) to the purge valve diaphragm.

diaphragm cannot be piers for at least 20 seconds,If the the valve should be

replaced.

EMISSION CONTROLS = 4-13

. Canister . Activated carbon element . Valve assy - pcv . Canister purge control valve . Valve assy bowl vent . Carburetor assy . Vapor restriction . Fuel tank, Aux. fuel tank . To TCC on A/T, to EGR on M/T

85774012

1 ; LARGE SIZE TWO CHAMBER CLOSED BOTTOM CANISTER

2} VAPOR VENT CONTROL VALVE PURGE CONTROL VALVE

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[4 ]CLEAN AIR TUBE “AIR CLNR” VAPOR FROM FUEL TANK [6 ]VAPOR FROM BOWL VENT TO MANIFOLD VACUUM SIGNAL [8 |TO PORTED VACUUM [9 |VAPOR TO PURGE LINE [10; FILTER 1; CARBON

[12, BOTTOM COVER 3; DUST CAP 4] AIR FLOW MOOS

TOT TT SE,

85774083

Fig. 29 Vapor cannister assembly

4-14

EMISSION CONTROLS

3. If the diaphragm does hold vacuum, try to blow again into the vapor purge port. An increased flow of air should be observed, if not replace the canister. Vapor Vent Control Valve

1. Connect a short length of hose to the vapor vent control valve’s fuel bowl port and attempt to blow through the valve. Air should pass through the valve freely. If not replace the canister. 2. Connect a hand vacuum pump to the vapor vent control valve vacuum port. Apply 51 kPa (15 in. Hg) to the valve diaphragm. If the diaphragm cannot hold vacuum for at least 20 seconds, the valve should be replaced.

3. If the diaphragm does hold vacuum, try to blow again into the valve’s fuel bowl port. Little or no air should pass through the valve, if not replace the canister. Thermostatic Vacuum Switch

1. Allow the switch to cool below the calibration temperature which is stamped on the valve. 2. Connect a hand vacuum pump to the output port of the TVS switch and apply 51 kPa (15 in. Hg) of vacuum. A leakage of up to 7 kPa (2 in. Hg) of vacuum in two minutes is allowable and does not indicate a defective switch. 3. Heat the TVS switch in some water above the calibration temperature.

=>Do not heat the TVS switch directly with an open flame. 4. Check if the valve opens (indicated by a loss of vacuum) at the calibration temperature. Canister Purge Solenoid

a. If the resistance is less than 20 ohms, the solenoid is

shorted. Replace the solenoid and the Engine Control Module (ECM). b. If the resistance is more than 20 ohms, the solenoid is

open. Replace the solenoid.

REMOVAL & INSTALLATION en

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Thermostatic Vacuum Switch

1. Drain the cooling system to below the switch level. 2. Disconnect and label the vacuum hoses from the switch. 3. Remove the thermostatic vacuum switch. To install: 4. Apply thread sealant on the replacement switch. 5. Tighten the thermostatic vacuum switch to 120 inch lbs. (14 Nm). 6. Connect the vacuum hoses. 7. Refill the cooling system. Canister Purge Solenoid

1. Disconnect the negative battery cable. ’ 2. Disconnect the electrical connectors and hoses from the solenoid. 3. Pull the solenoid away from the bracket and remove the assembly. To install: 4. Install the solenoid to the bracket by sliding it into place. 5. Connect the electrical connectors and the hoses. 6. Connect the negative battery cable.

Early Fuel Evaporation

1. Pull off the vacuum line to the top of the valve with the engine running. There should be vacuum in the line. Replace the line. No air should be escaping with the engine running at a steady idle. 2. Disconnect the harness connector from the solenoid and then turn the ignition on. Connect a voltmeter or test light between terminal A on the harness connector and ground. a. If 10 volts or greater is measured or the test light lights, the solenoid is getting power. b. If less than 10 volts is measured or the test light does not light, the solenoid is not getting power due to an open or short to ground in the wiring. 3. Measure the resistance across the solenoid by connecting an ohmmeter between the two terminals on the solenoid. Make sure that the solenoid is disconnected or a false reading may occur. The resistance of the solenoid should equal about 20 ohms.

ee.

2. Remove the vapor canister retaining nut. 3. Remove the canister from the vehicle. To install: 4. Install the canister. 5. Tighten the vapor canister retaining nut. 6. Reconnect the hoses to the canister. Refer to the vehicle emission control label, located in the engine compartment for proper routing of the vacuum hoses.

ae

Canister

1. Tag and disconnect the hoses from the canister.

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:

» See Figures 30 and 31

GENERAL INFORMATION The EFE system consists of an EFE valve at the flange of the exhaust manifold, an actuator, and a thermal vacuum switch (TVS). The TVS is located in the coolant outlet housing and controls vacuum application to the EFE actuator valve at the exhaust manifold. When the engine is cold, manifold vacuum is applied to the EFE actuator, which closes the EFE valve. When the EFE valve is closed, hot exhaust gases are routed to the base of the carburetor. The hot exhaust gases help warm the intake air temperature which improves fuel evaporation. This helps reduce the length of time that the choke is engaged. Once the engine coolant temperatures reach a set limit, the thermal vacuum switch closes to prevent vacuum from reaching the EFE actuator. Without vacuum applied, the EFE valve opens which reroutes exhaust out the exhaust system. If the EFE system does not operate when the engine is cold, stalling and stumbling may be experienced until the engine warms up. If the EFE valve were to get stuck in the Closed position, overheating and lack of power after the engine has warmed may be experienced.

EMISSION CONTROLS =4-15 EFE Valve and Actuator 1. Disconnect vacuum hose from EFE actuator.

«2 WARNING

EHAUST MANIFOLD

The EFE valve actuator and exhaust system components will be extremely hot and could severely burn you if the engine was recently run. Do not touch the EFE valve actuator or any exhaust components until they have cooled. 2. Check that the EFE valve actuator arm can be moved. Lubricate the valve if the valve will not move freely. 3. Start the engine and check for vacuum at the hose when the engine is cold. If no vacuum is detected check the hose and test the thermal vacuum switch. 4. Check if the EFE valve actuator closes (holds vacuum) by connecting a hand vacuum pump to the vacuum port of the valve. Apply 51 kPa (15 in. Hg) of vacuum. If the valve does not close, replace the EFE actuator.

EFE ACTUATOR

EXHAUST PIPE

REMOVAL & INSTALLATION EFE Valve and Actuator 85774013

Fig. 30 EFE valve installation

VENT (FIETERED) ——TOEFE VANE MANIFOLD VACUUM

=e ———————->-

1. Disconnect the vacuum hose from the valve. 2. Remove the exhaust pipe to manifold nuts and tension springs. 3. Lower crossover exhaust pipe and seal. Complete removal of the pipe is not always required. 4. Remove the EFE valve and actuator. To install: 5. Install EFE valve actuator with new seals and gaskets. 6. Install crossover exhaust pipe seal. 7. Reattach exhaust crossover pipe. Tighten exhaust pipe to manifold nuts to 15 ft. Ibs. (20 Nm). 8. Connect vacuum hose to EFE actuator valve. Thermal Vacuum Switch

» See Figure 96

85774014

Fig. 31 Thermal Vacuum Switch (TVS)

TESTING Thermal Vacuum Switch

1. 2. 3. To 4. 5. Nm). 6. 7.

Drain the cooling system to below the switch level. Disconnect and label the vacuum hoses from the switch. Remove the thermal vacuum switch. install: Apply thread sealant to the replacement switch. Tighten the thermal vacuum switch to 120 inch lbs. (14 Connect the vacuum hoses. Refill the cooling system.

1. Allow the switch to cool below the calibration temperature which is stamped on the valve. 2. Heat the thermal vacuum switch in some water above the calibration temperature. 3. Check if the valve closes (holds vacuum) at the calibration temperature by connecting a hand vacuum pump to the output port of the switch. Apply 51 kPa (15 in. Hg) of vacuum. A leakage of up to 7 kPa (2 in. Hg) of vacuum in two minutes is allowable and does not indicate a defective switch.

The purpose of the throttle return control system is to prevent an over rich condition during periods of deceleration. This

-*Do not heat the TVS switch directly with an open flame.

valve, and an engine speed switch.

Throttle Return Control » See Figures 32, 33, 34 and 35

is accomplished by keeping the throttle plate slightly open during deceleration, which helps maintain the air/fuel ratio at optimum efficiency. The Throttle Return Control (TRC) system consists of a throttle lever actuator, a solenoid vacuum control

4-16 EMISSION CONTROLS The engine speed switch monitors the engine speed (rpm) at

terminal ‘B‘ from the tach signal generated by the distributor. When a drop in engine speed (rpm) is detected the engine speed switch will apply a ground to the solenoid vacuum control valve. The solenoid vacuum control valve will now open and apply vacuum to the throttle lever actuator. When vacuum is applied to the throttle lever actuator, the plunger extends to hold the throttle plate slightly open. The system is designed to operate only when engine speed falls between 1700 and 1890 rpm. The throttle lever actuator is mounted on the carburetor. The solenoid vacuum control valve is mounted at the left rear of the engine above the intake manifold on the 6-cylinder, or on the thermostat housing mounting stud on the V8 engine. The engine speed switch can be found on the valve cover on V8 engines and on the right side of the engine block on the inline six cylinder engine.

TESTING TRC System Test

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1. Connect a tachometer to the distributor TACH terminal. 2. Start the engine and raise the engine speed to 1890 rpm. Observe the throttle lever actuator position. The actuator should be extended.

[1] NUT—TIGHTEN TO 28 N-m (20 FT. LBS.) ELECTRICAL CONNECTOR ENGINE SPEED SWITCH 85774016

Fig. 33 Engine speed switch locations

PLUNGER PRIMARY THROTTLE LEVER ACTUATOR-ON CARBURETOR

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ENGINE SPEED SWITCH SOLENOID VACUUM CONTROL VALVE

85774015

Fig. 32 TRC system schematic

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c. If the correct voltage is present at both components, go to the next step. 5. Check for solenoid vacuum control valve operation by grounding the solenoid-to-speed switch wire terminal at the solenoid connector with a jumper wire. This should cause the throttle lever actuator to extend, with the engine running.

CARBURETOR PIPE

a. If the lever actuator does not extend, remove the hose

ACCELERATOR SUPPORT

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Fig. 34 TRC valve assembly- inline six cylinder engine

SOLENOID CARBURETOR

from the solenoid side port which connects to the actuator hose. Check the port for obstructions or blockage. If the port is not plugged, replace the solenoid. b. If the lever actuator extends, go to the next step. 6. Ground the solenoid vacuum control valve-to-speed switch wire terminal at the switch. This should cause the throttle lever to extend with the engine running. a. lf the actuator does not extend, the wire between the speed switch and the solenoid is open and must be repaired. b. If the actuator does extend, check the speed switch ground wire for an open. If it is ok, replace the engine speed switch. 7. If the actuator is extended at all speeds: a. Remove the connector from the vacuum solenoid. b. If the actuator remains extended, check the solenoid side port orifice for blockage. If plugged, clear and reconnect the system and recheck. If the actuator is still extended, remove the solenoid connector; if the actuator does not re-

treat, replace the vacuum solenoid. 85774018

Fig. 35 TRC valve assembly-V8’s 3. Reduce the engine speed to 1700 rpm. Observe the throttle lever actuator position. The actuator should be retracted. a. If the throttle lever actuator operated as described, the TRC system is operating correctly. No further testing is necessary. b. If the throttle lever actuator operated as described but moved outside of the engine speed limits given, the speed switch is faulty and must be replaced. It cannot be adjusted. c. If the throtile lever actuator did not operate at all, further testing is required. Proceed to the next Step. d. If the throttle lever actuator is always extended, proceed to Step 7. 4. Check the voltage at the vacuum solenoid and the speed switch with a voltmeter. Connect the negative probe of the voltmeter to the engine ground and the positive probe to the voltage source wire on the component (see schematic). The positive probe can be inserted on the connector body at the wire side; it is not necessary to unplug the connector. Voltage should be 12 to 14 volts in both cases. a. If the correct voltage is present at one component but not the other, the engine wiring harness is faulty. b. If voltage is not present at all, check the engine harness connections and related wires for an open wire or connection. Repair as necessary.

c. If the actuator retracts with the solenoid connector off,

reconnect it and remove the speed switch connector. If the actuator retracts, the problem is in the speed switch, which should be replaced. If the actuator does not retract, the

solenoid-to-speed switch wire is shorted to ground in the wiring harness. Repair the short. Throttle Lever Actuator Test

1. Disconnect the valve-to-actuator hose at the valve and connect it to an external vacuum source. 2. Apply 20 in. Hg vacuum to the actuator and seal the vacuum source. If the vacuum gauge reading drops, the valve is leaking and should be replaced. 3. Check the throttle lever, shaft, and linkage for freedom of operation. ' 4. Start the engine and warm it to operating temperature. 5. Note the idle rpm. 6. Apply 20 in. Hg vacuum to the actuator and manually operate the throttle. Allow it to close against the extended actuator plunger. Note the engine rpm. 7. Release and reapply 20 in. Hg vacuum to the actuator and note the rpm at which the engine speed increases (do not assist the actuator). 8. If the engine speed obtained in Step 7 is not within 150 rom of that obtained in Step 6, then the actuator may be binding. If the binding cannot be corrected, replace the actuator.

9. Release the vacuum from the actuator. The engine speed should return to within 50 rom of the speed noted in Steps 5 and 6.

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EMISSION CONTROLS

Oxygen Sensor

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REMOVAL & INSTALLATION

1983-87 MODELS WITH ECM » See Figure 36 The oxygen sensor is a spark plug-shaped device that is screwed into the exhaust manifold on V8s and into the exhaust pipe on inline sixes. It monitors the oxygen content of the exhaust gases and sends as voltage signal to the Electronic Control Module (ECM). The ECM monitors this voltage and, depending on the value of the received signal, issues a command to the mixture control solenoid on the carburetor to adjust for rich or lean conditions. The proper operation of the oxygen sensor depends upon four basic conditions: 1. Good electrical connections — since the sensor generates low currents, good clean electrical connections at the sensor are a must.

2. Outside air supply — air must circulate to the internal portion of the sensor. When servicing the sensor, do not reStrict the air passages. 3. Proper operating temperatures — The ECM will not recognize the sensor signals until the sensor reaches approximately 600°F. 4. Non-leaded fuel — the use of leaded gasoline will damage the sensor very quickly.

e>Oxygen sensors are extremely sensitive to silicone. Exposure to silicone will contaminate and destroy the oxygen sensor. Be careful not to use silicone sealers or lubricants in any area such as the intake or exhaust manifolds to prevent contamination. A white colored element or tip is an indication that the oxygen sensor has been contaminated with silicone.

WARNING

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The sensor uses a permanently attached pigtail and connector. This pigtail should not be removed from the sensor. Damage or removal of the pigtail or connector could affect the proper operation of the sensor. Keep the electrical connector and louvered end of the sensor clean and free of grease. NEVER use cleaning solvents of any type on the sensor. The oxygen sensor may be difficult to remove when the temperature of the engine is below 120°F. Excessive force may damage the threads in the exhaust manifold or exhaust pipe. 1. Disconnect the electrical connector and any attaching hardware. 2. Remove the sensor. 3. Coat the threads of the sensor with a GM anti-seize compound 5613695 or equivalent, before installation. New sensors are pre-coated with this compound.

The GM anti-seize compound is NOT a conventional antiseize paste. The use of a regular paste may electrically insulate the sensor, rendering it useless. The threads MUST be coated with the proper electrically conductive anti-seize compound. 4. Install the sensor and torque to 30 ft. Ibs. Use care in making sure the boot is in the correct position to avoid melting it during operation. 5. Connect the electrical connector and attaching hardware if used.

Catalytic Converter

No attempt should be made to measure the output voltage of the sensor. The current drain of any conventional voltmeter would be enough to permanently damage the sensor. No jumpers, test leads, or other electrical connections should ever be made to the sensor. Use these tools ONLY on the ECM side of the harness connector AFTER the oxygen sensor has been disconnected.

(1] oxyGeN sensor - va

An oxidizing catalytic converter is used to control hydrocarbon and carbon monoxide emissions. Control is accomplished by placing a catalytic converter in the exhaust stream. As exhaust gases pass through the converter they undergo a chemical reaction before passing into the atmosphere. The catalyst in the converter which causes the reaction are beads which are coated with platinum and palladium. The chemical

[1] OxYGEN sensor -L6

85774019

Fig. 36 Oxygen sensor locations, V6 engine shown

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reaction involved is the oxidizing of hydrocarbons and carbon monoxide into water vapor and carbon dioxide.

REMOVAL & INSTALLATION

+ CAUTION Catalytic converter operating temperatures are extremely high. Outside converter temperatures can go well over +1,000°F (+538°C). Use extreme care when working on or around the catalytic converter.

1. Remove the heat shield. 2. Raise and safely support the truck. 3. Remove the clamps at the front and rear of the converter. 4. Cut the converter pipes at the front and rear of the converter and remove it. To install: 5. Install the exhaust pipe and tailpipe into the converter with sealer. 6. Install new U-bolts and clamps, check all clearances and tighten the clamps. 7. Install the heat shield. 8. Lower the truck.

Trapped Vacuum Spark This system is used to prevent a drop in vacuum to the distributor vacuum advance during cold engine operation, when the engine is accelerating. A Thermal Vacuum Switch (TVS) is used to sense engine coolant temperature. A check valve is installed in the vacuum line to the distributor. The other side of the check valve has two connections: one to manifold vacuum (at the carburetor base), and the other to the thermal vacuum switch. When the engine is cold, the TVS vacuum ports are closed. Manifold vacuum is routed through the check valve to the distributor. The check valve keeps the vacuum to the distributor at a high vacuum level, so that when the engine is accelerated, the vacuum to the distributor does not drop. This results in a constant spark advance. When the engine temperature reaches a predetermined value, the TVS ports open to allow manifold vacuum to the distributor, and the check valve operates only as a connector.

Exhaust Gas Recirculation » See Figures 37 and 38 The purpose of the EGR system is to control oxides of nitrogen which are formed during the peak combustion temperatures. The system feeds small amounts of exhaust gas back into the combustion chamber. Feeding back the exhaust gas lowers the combustion temperature which in turn lowers the oxides of nitrogen. If to much exhaust was reintroduced into the intake stream, combustion would not occur or would be inhibited. Symptoms of a open valve would be stalling after a cold start, engine stalls after deceleration, engine surging during a steady speed and rough idle. If the valve was always

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closed spark knock, engine overheating and possible emission test failure might occur. The EGR valve is operated by engine vacuum and generally is open only when the engine is warm and is operating above the idle speed. There are three types of valve control systems used to control EGR valve operation in General Motors trucks; the positive exhaust backpressure type, the negative exhaust backpressure type and the ECM vacuum solenoid controlled type. The ECM controlled EGR system is generally found only on trucks built for use in California. Both the negative and positive backpressure type valves use a thermal vacuum switch to prevent operation before the engine has warmed. The switch prevents vacuum from being applied to the valve when the engine coolant is cold. Both the negative and positive valves are designed to insure that the valve only operates above the engine idle speed and the amount the valve opens is not excessive. The choice of either a positive or negative backpressure valve is determined by measurement of the engine’s normal backpressure output. Negative valves are used on engines with relatively low backpressure; positive valves are used on engines with relatively high backpressure. If the valve is to be tested or replaced, it is important to know the type of installed. To identify the type of valve used, look on the top side of the valve. A ‘P’ will be stamped on the valve after the part number if the positive type is used or an ‘N‘ for a negative type valve. The positive backpressure type valve has an internal vacuum bleed hole that is open when exhaust pressure is low. As exhaust backpressure builds, the bleed valve closes allowing engine vacuum to be applied to open the EGR valve. The negative backpressure type EGR valve has an internal bleed hole that is closed when there is low exhaust backpressure. Engine vacuum opens the EGR valve. When engine vacuum increases combined with negative backpressure the vacuum bleed hole opens and the EGR valve will close. The ECM controlled EGR valve uses a solenoid valve to control the operation of the EGR valve. The ECM monitors the coolant temperature sensor signal and the throttle position sensor to determine when to operate the valve. Based on the coolant temperature and throttle position, the ECM will pulse the EGR vacuum solenoid on and off many times a second and varies the amount of ‘on’ time to vary the amount of gas recirculated. Since the ECM determines when the system operates, the level of exhaust backpressure is not important and therefore the system can use a simple standard ported EGR valve. On 6-cylinder engines, the EGR valve is located on the intake manifold adjacent to the carburetor. On small block V8 engines, the valve is located on the right rear side of the intake manifold adjacent to the rocker arm cover. Mark IV V8 EGR valves are located in the left front corner of the intake manifold in front of the carburetor.

TESTING Non-ECM Controlled EGR Valve

1. Hold top of EGR valve and try to rotate. If the valve can be rotated, replace it. 2. Apply parking brake and run engine at idle until it reaches normal operating temperature.

4-20

EMISSION CONTROLS returns to idle. If 6 inches (20 kPa) or greater of vacuum is measured, replace the EGR valve. 6. Check vacuum hoses for leaks or restrictions. If the hoses are ok, a defective thermal vacuum switch is the probable cause. ECM Controlled EGR Valve EGR VALVE

(@) vacuum cHAMBER

A EXHAUST GAS

[@] VALVE RETURN SPRING

[4] intake FLOW

[10] THERMAL VACUUM SWITCH

(6) vacuum PorT (7) tHrottLe vaive

COOLANT [12] DIAPHRAGM

85774084

Fig. 37 Non-ECM controlled EGR valve system

[1] [2] (3) [5]

EGR vatve exHaust Gas intake air b1aPHRAGM ELECTRONIC CONTROL MODULE

MANIFOLD VACUUM

[11] THROTTLE POSITION SENSOR [12] MANIFOLD PRESSURE SENSOR COOLANT SENSOR

TEMPERATURE

EGR CONTROL SOLENOID 85774085

Fig. 38 ECM controlled EGR valve system 3. Push up on underside of EGR valve diaphragm with engine idling. The engine rpm should drop if the system is working properly. If the engine rpm does not change, inspect and clean the EGR valve passages of deposits. If the valve is clean, the valve should be replaced. 4. Increase engine speed to approximately 2000 rpm and’ note position of EGR valve. Allow the engine speed to drop back down to idle and note position of valve. If the EGR valve moves, the valve is assumed OK. If the valve does not move,

go to the next Step. 5. Disconnect the vacuum hose from the EGR valve and connect a vacuum gauge to the hose. Measure the vacuum as engine speed is increased to approximately 2000 rpm and then

1. If the light is on, the Engine Control Module (ECM) has detected a problem and this problem must be repaired before proceeding. Refer to ‘Diagnostic Trouble Codes’ in this section for further information. 2. Hold top of EGR valve and try to rotate. If the valve can be rotated, replace it. 3. Apply parking brake and run engine at idle until it reaches normal operating temperature. 4. Push up on underside of EGR valve diaphragm with the engine idling. The engine rpm should drop. If it does not, inspect and clean the EGR valve passages of deposits. If the valve is clean, the valve should be replaced. 5. Increase engine speed to approximately 2000 rpm and note position of EGR valve. Allow the engine speed to drop back down to idle and note position of valve. If the EGR valve moves, the valve is assumed OK. If the valve does not move, go to the next Step. 6. Disconnect the vacuum hoses from the EGR valve solenoid. With the engine running, check that the hose connected to the carburetor or throttle body has vacuum. Unclog or replace the vacuum hose if no evidence of vacuum is present. 7. Bypass the solenoid valve by connecting the two hoses from the previous step together. Accelerate the engine a little while observing the EGR valve for movement. If the valve does not move at all, the hose or the EGR valve is defective, repair or replace as necessary. 8. Connect a test light across the wire terminals of the EGR valve solenoid while the engine is running at idle and warm. If the light flickers faintly, the solenoid valve is faulty. If the test light does not light, repair the open wiring to the solenoid. If the light stays on steady and doesn't flicker, check the wiring for a short to ground.

REMOVAL & INSTALLATION EGR Valve

1. Remove the air cleaner. 2. Disconnect the vacuum hose from the EGR valve. 3. Remove two bolts from EGR valve. Remove valve and gasket from manifold. 4. To install the EGR valve follow the procedure in reverse order. Be sure to replace the EGR valve gasket with a new gasket. EGR Vacuum Solenoid

1. Disconnect the negative battery cable. 2. Remove the air cleaner. 3. Disconnect the electrical connector and the two vacuum hoses. 4. Remove nut at solenoid bracket.

5. To install follow the procedure in the reverse order. Torque nut to 17 ft. Ibs. (24 Nm).

EMISSION CONTROLS LS

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Electronic Spark Timing (EST) System (California or fuel injected only) GENERAL DESCRIPTION The High Energy Ignition (HEI) system controls fuel combustion by providing the spark to ignite the compressed air/fuel mixture, in the combustion chamber, at the correct time. To provide improved engine performance, fuel economy and control of the exhaust emissions, the ECM controls distributor spark advance (timing) with the Electronic Spark Timing (EST) system. The standard High Energy Ignition (HEI) system has a modified distributor module which is used in conjunction with the EST system. The module has seven terminals instead of the four used without EST. Two different terminal arrangements are used, depending upon the distributor used with a particular engine application. To properly control ignition/combustion timing, the ECM needs to know the following information: . Crankshaft position. . Engine speed (rpm). . Engine load (vacuum). . Atmospheric (barometric) pressure. . Engine temperature. . Transmission gear position (certain models) — wn Oooh The EST system consists of the distributor module, ECM and its connecting wires. The distributor has four wires from the HEI module connected to a four terminal connector, which mates with a four wire connector from the ECM. These circuits perform the following functions: e Distributor reference at terminal B - This provides the ECM with rom and crankshaft position information. e Reference ground at terminal D - This wire is grounded in the distributor and makes sure the ground circuit has no voltage drop, which could affect performance. If this circuit is open, it could cause poor performance. e By-pass at terminal C - At approximately 400 rpm, the ECM applies 5 volts to this circuit to switch the spark timing control from the HE! module to the ECM. An open or grounded bypass circuit will set a Code 42 and the engine will

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The ECM uses information from the VAC and coolant sensors, in addition to rpm, in order to calculate spark advance as follows: -High VAC sensor output voltage would require MORE spark advance. -Cold engine would require MORE spark advance. -Low VAC sensor output voltage would require LESS spark advance. -Hot engine would require LESS spark advance.

INCORRECT EST OPERATION Detonation could be caused by high VAC sensor output, or high resistance in the coolant sensor circuit. Poor performance could be caused by low VAC sensor output or low resistance in the coolant sensor circuit.

HOW CODE 42 IS DETERMINED When the systems is operating on the HEI module with no voltage on the by-pass line, the HE! module grounds the EST signal. The ECM expects to sense no voltage on the EST line during this condition. If it senses voltage, it sets Code 42 and will not go into the EST mode. When the correct rom for EST is reached (approximately 400 rpm), the ECM applies 5 volts to the by-pass line and the EST should no longer be grounded in the HE! module, so the EST voltage should be varying. If the by-pass line is open, the HE! module will not switch to the EST mode, so the EST voltage will be low and Code 42

will be set. If the EST line is grounded, the HEI module will switch to

the EST, but because the line is grounded, there will be no EST signal and the engine will not operate. A Code 42 may or may not be set.

Electronic Spark Control (ESC) System (California or fuel injected only) GENERAL DESCRIPTION

run at base timing, plus a small amount of advance built into

the HEI module. e EST at terminal A - This triggers the HE! module. The ECM does not know what the actual timing is, but it does know when it gets its reference signal. It then advances or retards the spark timing from that point. Therefore, if the base timing is set incorrectly, the entire spark curve will be incorrect. An open circuit in the EST circuit will set a Code 42 and cause the engine to run on the HE! module timing. This will cause poor performance and poor fuel economy. A ground may set a Code 42, but the engine will not run.

The Electronic Spark Control (ESC) operates in conjunction with the Electronic Spark Timing (EST) system and modifies (retards) the spark advance when detonation occurs. The retard mode is held for approximately 20 seconds after which the spark control will again revert to the Electronic Spark Timing (EST) system. There are three basic components of the Electronic Spark Control (ESC) system; the detonation sensor, distributor and the controller. Should a Code 43 be set in the ECM memory, it would indicate that the ESC system retard signal has been sensed by the ECM for too long a period of time. When voltage at terminal L of the ECM is low, spark timing is retarded. Normal voltage in the non-retarded mode is approximately 7.5 volts or more.

4-22

EMISSION CONTROLS

DETONATION SENSOR The detonation sensor detects the presence (or absence) and intensity of the detonation (ping) by the vibration characteristics of the engine. The output is an electrical signal that goes to the controller. A sensor failure would allow no spark retard.

DISTRIBUTOR LL

The distributor is an HEI/EST unit with an electronic module, modified so it can respond to the ESC controller signal. This command is delayed when detonation is occurring, thus providing the level of spark retard required. The amount of spark retard is a function of the degree of detonation.

CONTROLLER The Electronic Spark Control (ESC) controller processes the sensor signal into a command signal to the distributor, to ad-

just the spark timing. The process is continuous, so that the presence of detonation is monitored and controlled. The controller is a hard wired signal processor and amplifier which operates from 6-16 volts.

BASIC IGNITION TIMING Basic ignition timing is critical to the proper operation of the ESC system. Always follow the Vehicle Emission Control Information label procedures when adjusting ignition timing. Some engines will incorporate a magnetic timing probe hole for use with special electronic timing equipment. Consult the manufacturer's instructions for the use of this electronic timing equipment.

Computer Command Control (CCC) System (California or fuel injected engines only) GENERAL INFORMATION The CCC System monitors up to nineteen engine/vehicle operating conditions which it uses to control up to nine engine and emission control systems. This system controls engine operation and lowers the exhaust emissions while maintaining good fuel economy and driveability. The Electronic Control Module (ECM) is the brain of the CCC system. The ECM controls as many as 12 engine related systems constantly adjusting them for maximum efficiency. In addition to maintaining the ideal air/fuel ratio and adjusting ignition timing, the CCC System also controls the Air Management System, the transmission torque converter clutch (certain automatic transmission models only), idle speed, Evaporative Emissions System, the

EGR valve operation and the early fuel evaporative (EFE) system.

The CCC system is primarily an emission control system, designed to maintain a 14.7:1 air/fuel ratio under all operating conditions. When this ideal air/fuel ratio is maintained the catalytic converter can control oxides of nitrogen (NOx), hydrocarbon (HC) and carbon monoxide (CO) emissions. There are two operation modes for CCC System: closed loop and open loop fuel control. Closed loop fuel control means the oxygen sensor is controlling the carburetor or throttle body delivered air/fuel mixture ratio. Under open loop fuel control operating conditions (wide open throttle, engine and/or oxygen sensor cold), the oxygen sensor has no effect on the air/fuel mixture. e>On some engines, the oxygen sensor will the engine is idling, putting the system into operation. To restore closed loop operation, gine at part throttle and accelerate from idle tle a few times.

cool off while open loop run the ento part throt-

The carburetor mixes air and gasoline into a combustible mixture before delivering it to the engine. However, carburetors have reached a point where they can no longer control the airfuel mixture sufficiently close to the ideal 14.7:1' ratio for most operating conditions. Therefore, an electric solenoid has been

incorporated into the carburetor to control the air-fuel ratio. The solenoid is connected to the ECM. The ECM provides a controlling or adjustment signal to the solenoid. The solenoid controls the metering rod(s) and a idle air bleed valve to maintain the ideal air-fuel ratio throughout the operating range of the engine. Since conditions that would effect the air fuel ratio vary widely, the ECM monitors conditions through several sensors.

This provides for proper adjustment of the solenoid, for all driving conditions. One of the most important sensors that the ECM relies on for controlling mixture is located in the exhaust stream and is known as the oxygen sensor or simply an Oz sensor. The sensor functions when the engine’s exhaust temperature rises above 600°F (316°C). There is a direct relationship between the mixture delivered by the carburetor and the amount of oxygen left in the exhaust gases. The O» sensor detects the level of oxygen in the exhaust and signals the ECM by varying the voltage signal to the ECM. From this signal, the ECM is able to calculate whether the mixture is too rich or too lean and will adjust the mixture control solenoid accordingly. This process goes on continually and is referred to as Closed Loop operation. Closed loop operation tries to maintain the optimum 14.7:1 air/fuel mixture to the engine. In the morning when the engine is cold, if the system keep the air/fuel mixture at the 14.7:1 ratio, the engine wouldn’t run very well. When the engine is cold, it has to have a richer mixture. An automatic choke is used to give the engine a richer mixture until it is up to normal operating temperature. In addition to the choke, a temperature sensor located in the water jacket of the engine is used by the ECM to monitor engine temperature. When the temperature sensor signal indicates that the engine is cold, the ECM will ignore the oxygen sensor signal. During the period that the O. sensor signals are ignored the ECM is running in a mode known as open loop. During this open loop period, the ECM adjusts the mixture control solenoid to deliver a richer mixture based on a preset program retained in the ECM’s memory. The ECM also uses

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information from other sensors during cold start operation. After the engine has warmed up to normal operating temperature, based on the temperature sensor's signal, the ECM will switch to closed loop operation. While the oxygen and coolant temperature sensor influence the ECM the most in control of the fuel mixture, there are three other factors which influence the ECM. One of these is the load that is placed upon the engine. When an engine is working hard, such as pulling a heavy load up a long grade, it requires a richer air/fuel mixture. This is different from a vehicle that is operating in a cruise condition on a level highway at a constant rate of speed. Manifold vacuum is used to determine engine load. A vacuum sensor is used to detect changes in the manifold vacuum which are signaled to the ECM. As load changes occur, the vacuum signal varies. The ECM takes this varying signal into account when determining what mixture the carburetor should be delivering to the engine. Another factor in determining what air/fuel mixture should be is the amount of throttle opening. The more throttle opening at any given time, the richer the mixture required by the engine. On most applications, a Throttle Position Sensor (TPS) is used to signal the ECM as to the position of the throttle, whether it is at idle, part throttle or wide open throttle. The final factor in the fuel mixture equation is the speed the engine is running. Certainly, when an engine is operating at 600 rpm, it doesn’t need as much fuel as it does when it is operating at 4000 rpm. Therefore, a tachometer signal from the distributor is fed to the ECM for calculation in the fuel mixture equation. The ECM is a reliable solid state computer, protected in a metal box and located in the cab. It is used to monitor and

control all the functions of the CCC System. As explained previously the ECM can perform several functions at the same time but it also has the ability to detect certain faults within the CCC system. Generally when it detects a fault in the system the ECM will do three things; one is it will warn the driver by turning on the ‘CHECK ENGINE‘ or ‘SERVICE ENGINE SOON’ light on the instrument panel, second it will try to compensate for the fault in many cases and third it will record what system or circuit is faulty in its memory. When the engine is started, the CHECK ENGINE light will remain on for a few seconds,

then turn off. This is normal operation but if the CHECK ENGINE light remains on, the self-diagnostic system has detected a problem. The ECM records the fault in it’s memory in the form of a diagnostic trouble code. The diagnostic trouble codes recorded in the ECM’s memory can later be accessed to aid in diagnosis of the Computer Command System fault. It should be understood though, that as powerful as the ECM is as a computer it does have limitations and cannot detect all the possible failures that could be encountered.

SCAN TOOLS Although stored codes may be read with only the use of a small jumper wire, the use of a hand-held scan tool such as GM's TECH 1 or equivalent is recommended. There are many manufacturers of these tools; a purchaser must be certain that the tool is proper for the intended use. The scan tool allows any stored codes to be read from the ECM memory. The tool also allows the operator to view the

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data being sent to the ECM while the engine is running. A scan tool makes collecting information easier; the data must be

correctly interpreted by an operator familiar with the system. An example of the usefulness of the scan tool may be seen in the case of a temperature sensor which has changed its electrical characteristics. The ECM is reacting to an apparently warmer engine (causing a driveability problem), but the sensor voltage has not changed enough to set a fault code. Connecting the scan tool, the voltage signal being sent to the ECM may be viewed; comparison to either a chart of normal values or a known good vehicle reveals the problem quickly.

TROUBLESHOOTING Diagnosis of a driveability and/or emission problem requires attention to detail and following the diagnostic procedures in the correct order. Resist the temptation to perform any repairs before performing the preliminary diagnostic steps. In many cases this will shorten diagnostic time and often cure the problem without further testing.

Visual/Physical Underhood Inspection This is possibly the most critical step of diagnosis. A detailed examination of connectors, wiring and vacuum hoses can often

lead to a repair without further diagnosis. Performance of this step relies on the skill of the technician performing it; a careful inspector will check the undersides of hoses as well as the integrity of hard-to-reach hoses blocked by the air cleaner or other component. Wiring should be checked carefully for any sign of strain, burning, crimping, or terminal pull-out from a connector. Checking connectors at components or in harnesses is required; usually, pushing them together will reveal a loose fit. Diagnostic Circuit Check This step is used to check that the on-board diagnostic system is working correctly. A system which is faulty or shorted may not yield correct codes when placed in the Diagnostic Mode. Performing this test confirms that the diagnostic system is not failed and is able to communicate through the dash warning lamp. Reading Trouble Codes Once the integrity of the system is confirmed, enter the Diagnostic Mode and read any stored codes. To enter the diagnostic mode: 1. Turn the ignition switch OFF. Locate the Assembly Line Diagnostic Link (ALDL), usually under the instrument panel. It may be within a plastic cover or housing labeled DIAGNOSTIC CONNECTOR. This link is used to communicate with the ECM. 2. The code(s) stored in memory may be read either through the flashing of the dashboard warning lamp or through the use of a hand-held scan tool. If using the scan tool, con-

nect it correctly to the ALDL. 3. If reading codes via the dash warning lamp, use a small jumper wire to connect Terminal B of the ALDL to Terminal A. As the ALDL connector is viewed from the front, Terminal A is on the extreme right of the upper row; Terminal B is second from the right on the upper row.

4-24

EMISSION CONTROLS

4. After the terminals are connected, turn the ignition switch to the ON position but do not start the engine. The dash . warning lamp should begin to flash Code 12. The code will display as one flash, a pause and two flashes. Code 12 is not a fault code. It is used as a system acknowledgment or handshake code; its presence indicates that the ECM can commu-

nicate as requested. Code 12 is used to begin every diagnostic sequence. Some vehicles also use Code 12 after all diagnostic codes have been sent. 5. After Code 12 has been transmitted 3 times, the fault

codes, if any, will each be transmitted 3 times. The codes are stored and transmitted in numeric order from lowest to highest. ->The order of codes in the memory does not indicate the order of occurrence.

6. Switch the ignition OFF when finished with code retrieval or scan tool readings. e>Due to increased battery draw, do not allow the vehicle to remain in the Diagnostic Mode for more than 30 minutes. If longer periods are necessary, connect a battery charger.

Clearing Trouble Codes Stored fault codes may be erased from memory at any time by removing power from the ECM for at least 30 seconds. It may be necessary to clear stored codes during diagnosis to check for any recurrence during a test drive, but the stored codes must be written down when retrieved. The codes may

still be required for subsequent troubleshooting. Whenever a repair is complete, the stored codes must be erased and the vehicle test driven to confirm correct operation and repair.

=The ignition switch must be OFF any time power is disconnected or restored to the ECM. Severe damage may result if this precaution is not observed. Depending on the electric distribution of the particular vehicle, power to the ECM may be disconnected by removing the ECM fuse in the fusebox, or disconnecting the positive battery terminal. Disconnecting the battery cables to clear codes is not recommended as this will also clear other memory data in the vehicle such as radio presets or clock. Field Service Mode

lf ALDL terminal B is grounded to terminal A with the engine running, the system enters the Field Service Mode. In this mode, the dash warning lamp will indicate whether the system is operating in open loop or closed loop. If working in open loop, the dash warning lamp will flash rapidly 2'/2 times per second. In closed loop, the flash rate slows to once per second. Additionally, if the system is running lean in closed loop, the lamp will be off most of the cycle. A rich condition in closed loop will cause the lamp to remain lit for most of the 1 second cycle. When operating in the Field Service Mode, additional codes cannot be stored by the ECM. The closed loop timer is bypassed in this mode.

DIAGNOSTIC TROUBLE CODES — GASOLINE ENGINES The following is a list of possible diagnostic trouble codes that could be stored in the Electronic Control Module’s (ECM) memory. It should be noted that a diagnostic trouble code does not identify that a particular component has failed, but a problem in the circuit of that component has occurred. Therefore, if a code is found to be set in the ECM’s memory, the

related circuit must be checked completely. Be sure to perform the visual inspection before proceeding with additional testing and pay particular attention to wiring terminal connections at connectors for loose or corroded connections. CODE 12 — No engine speed sensor reference pulses are being received by the ECM. This code is not stored in memory and will flash only while the fault is present. This code is normal when the ignition is on and the engine is not running. Code 13 — The ECM has detected a problem in the oxygen sensor circuit. The engine must run at part throttle for at least four minutes before this code will set. Code 14 — The ECM has detected a short in the coolant temperature sensor circuit. The engine must be running for at least two minutes before this code will set. Code 15 — The ECM has. detected a open in the coolant temperature sensor circuit. The engine must be running for at least two minutes before this code will set. Code 21 — The ECM has detected that the throttle position sensor circuit voltage is high. This is and indication that the throttle position sensor is out of adjustment or an open in the circuit wiring has occurred. The engine must run for a least 30 seconds at idle before this code will set in the ECM’s memory.

Code 22 — The ECM has detected that the throttle position sensor circuit voltage is low. This is an indication that the throttle position sensor circuit is shorted to ground. The engine must run for at least 2 minutes at 1250 rpm before this code will set in the ECM’s memory. Code 23 — The ECM has detected a short or open in the mixture control solenoid circuit on carbureted engines or the Manifold Air Temperature (MAT) signal is high indicating a open circuit on fuel injected vehicles. Code 24 — No vehicle speed sensor signals are being received by the ECM. This is an indication that the circuit has an open or is shorted to ground. For this code to set, the vehicle must operate at any speed for 10 seconds. Code 25 — The ECM has detected that the Manifold Air Temperature (MAT) signal is low indicating a short to ground on fuel injected vehicles. Code 32 — The barometric pressure circuit signal voltage is low. Code 33 — The ECM has detected low vacuum in the Manifold Absolute Pressure (MAP) sensor circuit. Code 34 — The ECM has detected a problem in the vacuum sensor or the manifold absolute pressure sensor circuit. The engine must run for at least 2 minutes at curb idle before this code will set in the ECM’s memory. Code 35 — The ECM has detected a problem with the idle speed control circuit. Code 41 — No distributor reference pulses to the ECM at specified engine vacuum.

EMISSION CONTROLS Code 42 — Electronic spark timing grounded or open. Code 43 — Electronic spark control a time period; causes a retard in the Code 44 — The ECM has detected The engine must run for two minutes before this code will set. Code 45 — The ECM has detected The engine must run for two minutes before this code will set.

bypass circuit is

Code 51 — Faulty or improperly installed PROM or calibration chip in the ECM. The ignition must be on for approximately 10 seconds before this code will set. Code 53 — Exhaust Gas Recirculation (EGR) valve vacuum sensor circuit. The ECM has seen an improper EGR valve vacuum. Code 54 — The ECM has detected a short in the mixture control solenoid and or a faulty ECM. Code 55 — The ECM has detected a problem with itself. Replacement of the ECM is required.

retard signal for too long electronic spark timing. a lean exhaust condition. in closed loop operation

a rich exhaust condition. in closed loop operation

DIESEL ENGINE EMISSIONS CONTROLS

4-25

~

Crankcase Ventilation » See Figures 39, 40, 41 and 42 A Crankcase Depression Regulator Valve (CDRV) is used to regulate (meter) the flow of crankcase gases back into the engine to be burned. The CDRV is designed to limit vacuum in the crankcase as the gases are drawn from the valve covers through the CDRV and into the intake manifold (air crossover). Fresh air enters the engine through the combination filter, check valve and oil fill cap. The fresh air mixes with blow-by gases and enters both valve covers. The gases pass through a filter installed on the valve covers and are drawn into connecting tubing. Intake manifold vacuum acts against a spring loaded diaphragm to control the flow of crankcase gases. Higher intake vacuum levels pull the diaphragm closer to the top of the outlet tube. This reduces the amount of gases being drawn from the crankcase and decreases the vacuum level in the crankcase. As the intake vacuum decreases, the spring pushes the diaphragm away from the top of the outlet tube allowing more gases to flow to the intake manifold.

CRANKCASE

VENTILATION SYSTEM SCHEMATIC V-TYPE DIESEL ENGINE WITH DEPRESSION REGULATOR VALVE

1. Crankcase depression regulator 2. Ventilation filter 3. Breather cap 85774020

Do not allow any solvent to come in contact with the diaphragm of the Crankcase Depression Regulator Valve because the diaphragm will fail.

REMOVAL & INSTALLATION . Loosen the clamps from the hoses. . Remove the two hoses.

. Remove the two mounting bolts from the valve. . Remove the CDR valve. . Installation is the reverse of removal.

wor or —

Exhaust Gas Recirculation (EGR) » See Figures 43, 44, 45 and 46

GENERAL INFORMATION To lower the formation of nitrogen oxides (NOx) in the exhaust, it is necessary to reduce combustion temperatures. This is done in the diesel, as in the gasoline engine, by introducing

Fig. 39 Diesel crankcase ventilation system flow, 350 shown exhaust gases into the cylinders through the EGR valve. The EGR system is not used on vehicles with heavy duty emissions system. Except California Models On the 379 diesel, an Exhaust Pressure Regulator (EPR) valve and solenoid operate in conjunction with the EGR valve. The EPR valve is located between the exhaust pipe and manifold, it’s job is to increase exhaust backpressure in order to increase EGR flow (to reduce nitrous oxide emissions) during idle. The EPR valve increases exhaust backpressure when it is closed. The EPR valve is usually open, and the EPR solenoid valve is normally closed. When the EPR solenoid valve is energized by the B+ wire from the Throttle Position Switch (TPS), the EPR solenoid valve opens, allowing vacuum to applied to the EPR valve, closing it. This occurs at idle. As the throttle is opened to a calibrated angle, the TPS de-energizes the EPR solenoid valve, cutting off vacuum to the EPR valve and thus closing the valve.

4-26

EMISSION CONTROLS

. . . . .

Crankcase Ventilation Brace clip Ventilation Crankcase

depression regulator (CDR) filter

pipes depression regulator (CDR)

6. 7. 8. 9.

L.H. valve cover Bracket Air crossover Air crossover to regulator valve pipe 85774021

Fig. 40 Diesel crankcase ventilation system components, 350 shown

. Hose to Intake

. Blowby Gases from the Crankcase . Clamps

. Bolts . CDR Valve 85774086

Fig. 41 Diesel crankcase ventilation system components, 379 shown EPR VALVE EPR SOLENOID

EGR SOLENOID INJECTION PUMP

VACUUM PUMP

CRANKCASE DEPRESSION REGULATOR 85774022

Fig. 42 379 diesel emissions components

EMISSION CONTROLS = 4-27 California models

EPR SOLENOID

On California models, the EGR system is controlled differ-

ently but the theory of operation is similar to the system used in the 49 states. The EGR/EPR solenoid valve assembly’s operation in California models is controlled by the Engine Control Module (ECM). The ECM controls the EGR solenoid to regulate the vacuum applied to the EGR valve. The vacuum is applied in an on and off fashion in order to precisely regulate EGR operation. The ECM calculates the amount of EGR that is needed based on inputs from the engine speed sensor and the throttle position sensor. The ECM is programmed to calculate the on and off time of EGR solenoid operation based on these two sensor inputs. To insure correct EGR function, the ECM also monitors the amount of absolute pressure in the EGR vacuum line using a the manifold absolute pressure sensor. If the variation in EGR operation is beyond what the ECM can correct for, the ECM will record a diagnostic trouble code in memory and the system will go into default mode. When the ECM recognizes that no EGR operation is needed, the ECM will turn on the EGR vent solenoid to allow venting of the EGR valve vacuum. The ECM will also energize the EPR solenoid valve to close the EPR valve whenever the engine is at idle.

TESTING Generally, heavy black exhaust is an indication that the exhaust gas recirculation system is malfunctioning.

EGR SOLENOID

EPR PIPE

EPR VALVE

85774023

Fig. 44 Exhaust pressure regulator valve and solenoid, 379 diesels EGR Operational Test Non-California Models 1. Start the engine and run until normal operating temperature is reached. 2. Carefully remove the air cleaner to observe the EGR valve operation with the engine idling. The EGR valve should be open. An open valve’s head will be in the up position and noticeable exhaust intake can be heard. If the valve is not open, check vacuum hoses and all electrical connections in the system.

3. valve 4. hose (6.75

Disconnect the vacuum hose from the EGR valve. The should close and exhaust noise should be reduced. Connect a vacuum gauge to the EGR valve vacuum with the engine idling. A reading of 20 inches of vacuum kPa) should be measured. If the reading is lower, check

EGR VALVE INTAKE RUNNER

EXHAUST GASES [4] EPR VALVE TO 700 R4 TRANSMISSION CONVERTER CLUTCH

[6] INJECTION PUMP +12 VOLTS (PINK)

THROTTLE POSITION SWITCH [9] EPR SOLENOID

VACUUM PUMP

EGR SOLENOID EPR WIRE (BLUE)

EGR WIRE (YELLOW)

85774087

Fig. 43 Non-California diesel EGR system schematic

4-28

EMISSION CONTROLS

ASSEMBLY

85774024

9. With the ignition on, check the blue wire to the throttle position switch for 12 volts. If no voltage is measured, the throttle position switch adjustment should be checked (Refer to TPS Adjustment listed below). Replace the switch if adjustment does not correct the problem. 10. With the ignition on, leave the voltmeter connected to

85774025

Fig. 46 Diesel Vacuum Regulator Valve (VRV) is mounted to injection pump the output of the vacuum pump. If the pump is ok, replace the hoses. 5. If the vacuum at the EGR valve is ok, connect and disconnect the vacuum hose to the EGR valve while allowing the engine to idle. While doing this, observe the EGR valve operation. If it appears to stick or bind, replacement of the valve is required. 6. Manually operate the throttle lever at the injection pump through 15 to 20 degrees of travel. The EGR valve should remain open. 7. Manually operate the throttle lever at the injection pump beyond 20 degrees of travel. The EGR valve should close. 8. Turn the engine off. Check the pink wire to the throttle position switch for 12 volts when the ignition is on. If no voltage is measured, repair the wiring to the switch.

the blue wire at the throttle position switch. Operate the throttle through 20 degrees of travel. At approximately 15 degrees, the voltage should drop to 0 volts. If voltage is measured, the throttle position switch adjustment should be checked (Refer to TPS Adjustment listed below). Replace the switch if adjustment does not correct the problem. 11. Connect the voltmeter to the yellow wire at the throttle position switch. Operate the throttle lever beyond 20 degrees of travel. 12 volts should be measured when the throttle lever is opened beyond the 20 degrees. If no voltage is measured, the throttle position switch adjustment should be checked (Refer to TPS Adjustment listed below). Replace the switch if adjustment does not correct the problem. 12. Check to see that the electrical connections are made at the EGR and EPR solenoid assemblies and that the hoses are routed correctly and connected to the solenoids. 13. If the system checked out ok in the previous Steps, the EGR or EPR solenoid valve is inoperative and should be replaced.

Exhaust Gas Recirculation (EGR) Valve In order to check EGR valve operation directly, apply vacuum to vacuum port on the valve. The valve should be fully open with 10.5 inches of vacuum applied, and closed when vacuum is below 6 inches.

EMISSION CONTROLS SSS

OS

ST

SS

PT

DIENT

NS

SA

SG

IES

A aSAR

NE SEESSRT SCE TST

A

4-29 pS

SST OUD ATG

REMOVAL & INSTALLATION

provide vacuum, a vacuum pump is mounted in the location occupied by the distributor in a gasoline engine. This pump supplies vacuum for the EGR valve system, air conditioning

EGR Valve

servos, the cruise control servos, and the transmission vacuum

1. Remove the air cleaner. 2. Disconnect the vacuum hose from the EGR valve. 3. Remove the two stud bolts from the EGR valve. Remove the valve from manifold. 4. To install the EGR valve, follow the removal procedure in reverse order.

modulator, where required. The pump is a diaphragm type pump which needs no maintenance. It is driven by a drive gear on its lower end which meshes with gear teeth on the end of the engine camshaft.

REMOVAL & INSTALLATION

EGR/EPR Vacuum Solenoid

1. Disconnect the negative battery cable. 2. Disconnect the electrical connectors and vacuum hoses. 3. Remove bolt at solenoid bracket.

4. To install, follow the removal procedure in the reverse order.

ADJUSTMENT Throttle Position Switch (TPS) This procedure is for Non-California models only. California models do not use a throttle position switch but a throttle position sensor. 1. Disconnect the throttle position switch connector. 2. Loosen the mounting screws that hold the throttle position switch. 3. Connect an ohmmeter test light to the ‘IGN‘ terminal (pink wire) and the ‘EGR* terminal (yellow wire) of the throttle position sensor.

4. Insert the specified gauge block for the ‘switch closed’ position between the gage boss on the injection pump and the wide open stop screw on the throttle shaft. Refer to the emission control label on the truck for the ‘switch closed’ gauge block specification. 5. Rotate the throttle lever and hold the wide open stop against the gauge block. 6. Rotate the throttle position switch until there is continuity between the terminals. 7. Hold the throttle position and tighten the mounting screws to 53 inch Ibs. (6 Nm). 8. Return the throttle lever to the idle position and remove the gauge block. 9. Insert the specified gauge block for the ‘switch open’ position between the gauge boss on the injection pump and the wide open stop screw. Refer to the emission control label on the truck for the ‘switch open‘ gauge block specification. Rotate the throttle lever against the block. There should be no continuity measured. If there is continuity, repeat Steps 1 thru 9, 10. Remove the gauge block and ohmmeter. 11. Connect the throttle position switch connector.

1. Remove the air cleaner. 2. Remove the vacuum hose from the pump outlet. 3. Remove the air cleaner, and cover the intake manifold. 4, Remove the vacuum pump clamp and bolt and then remove the pump. To install: 5. Install a new gasket. 6. Install the pump assembly making sure that the drive gear meshes with camshaft gear. 7. Rotate the pump so the inlet tube faces the front of the engine. The pump should be on a 20 degree angle. 8. Tighten bolt and bracket to 20 ft. lbs.(27 Nm). 9. Connect the vacuum hose to the pump outlet. 10. Install the air cleaner.

Diesel Electronic Control System California Only The Diesel Electronic Control (DEC) system is used on 6.2L (379) engines built for use in California to control the exhaust gas recirculation system, exhaust pressure regulation system and the transmission converter clutch. The primary component in the system is the diesel Electronic Control Module (ECM). To effectively control all of the systems, the diesel ECM monitors several engine parameters. These parameters include the engine rom signal which is derived from the engine speed sensor, the vacuum level in the EGR system which is sensed using a manifold absolute pressure sensor, the throttle position which is sensed through the throttle position sensor, and vehi-’ cle speed signal which is derived from the vehicle speed

sensor. The ECM is a reliable solid state computer, protected in a metal box and located in the cab. It is used to monitor and control all the functions of the Diesel Electronic Control System. As explained previously, the ECM can perform several functions at the same time but it also has the ability to detect certain faults within the system. When it detects a fault in the system, the ECM will record what system or circuit that is faulty in memory. The ECM records the fault in the form of a diagnostic trouble code. The diagnostic trouble codes recorded in the ECM’s memory can later be accessed to aid in diagnosis of the problem. It should be understood that the ECM can not detect all the possible failures that may be encountered.

TROUBLESHOOTING Since the air crossover and intake manifold in a diesel engine is unrestricted (unlike a gasoline engine which has throttle plates creating a venturi effect) there is no vacuum source. To

Diagnosis of a driveability and/or emissions problems requires attention to detail and following the diagnostic proce-

4-30

EMISSION CONTROLS

dures in the correct order. Resist the temptation to perform any repairs before performing the preliminary diagnostic steps. In many cases this will shorten diagnostic time and often cure the problem without further testing. Perform diagnosis in the order listed below.

Visual/Physical Underhood Inspection

This is possibly the most critical step of diagnosis, and should be performed first. A detailed examination of connectors, wiring and vacuum hoses can often lead to a repair without further diagnosis. Performance of this step relies on the skill of the technician performing it; a careful inspector will check the undersides of hoses as well as the integrity of hardto-reach hoses blocked by the air cleaner or other component. Wiring should be checked carefully for any sign of strain, burning, crimping, or terminal pull-out from a connector. Checking connectors at components or in harnesses is required; usually, pushing them together will reveal a loose fit.

Reading Diagnostic Trouble Codes Unlike the Computer Control Command System found on gasoline engines, the diagnostic codes stored in the Diesel Electronic System can not be accessed using a simple jumper

wire. The diesel diagnostic check tool or equivalent must be used to access any stored codes in the ECM’s memory. To use the check tool, follow the operating instructions supplied with the unit.

Clearing Trouble Codes Stored fault codes may be erased from memory at any time by removing power from the ECM for at least 30 seconds. It may be necessary to clear stored codes during diagnosis to check for any recurrence during a test drive, but the stored

codes must be written down when retrieved. The codes may still be required for subsequent troubleshooting. Whenever a repair is complete, the stored codes must be erased and the vehicle test driven to confirm correct operation and repair.

=>The ignition switch must be OFF any time power is disconnected or restored to the ECM. Severe damage may result if this precaution is not observed. Depending on the electric distribution of the particular vehicle, power to the ECM may be disconnected by removing the ECM fuse in the fusebox, or disconnecting the positive battery terminal. Disconnecting the battery cables to clear codes Is not recommended, as this will also clear other memory data in the vehicle such as radio presets or clock.

fn)/-Xe}N(olsy a(om f= {0)0) =|Wigexe) b) cee 9)|=A}4Wl=1y\(€]))\|= Unlike the Computer Control Command System found on gasoline engines, the diagnostic codes stored in the Diesel Electronic System can not be accessed using a simple jumper wire. The diesel diagnostic check tool or equivalent must be used to access any stored codes in the ECM’s memory. The following is a list of possible diagnostic trouble codes that could be stored in the electronic control module’s memory. It should be noted that a diagnostic trouble code does not identify that a particular component has failed but a problem in the circuit of that component has occurred. Therefore, if a code is found to be set in the ECM’s memory, the related Circuit must be checked completely. Be sure to perform the visual inspection before proceeding with additional testing and pay particular attention to wiring terminal connections at connectors for loose or corroded connections. CODE 12 — No engine speed sensor reference pulses are being received by the ECM. This code is not stored in memory and will flash while the fault is present. This code is normal when the ignition is on and the engine is not running. Code 21 — The ECM has detected that the throttle position sensor circuit voltage is high. This is and indication that the throttle position sensor is out of adjustment or an open in the Circuit wiring has occurred. The engine must run for a least 30 seconds at idle before this code will set in ECM memory. Code 22 — The ECM has detected that the throttle position sensor circuit voltage is low. This may be an indication that

-VACUUM DIAGRAMS

:

Below is a listing of vacuum diagrams for most of the engine and emissions package combinations covered by this manual. Because vacuum circuits will vary based on various engine and vehicle options, always refer first to the vehicle emission

the throttle position sensor circuit is shorted to ground. The engine must run for at least 2 minutes at 1250 rpm before this code will set in ECM memory. Code 24 — No vehicle speed sensor signals are being received by the ECM. This is an indication that the circuit has an open or is shorted to ground. For this code to set, the vehicle must operate at any speed for 10 seconds. Code 31 — The absolute pressure circuit (MAP sensor) signal voltage is low. The engine must be run at curb idle for at least 10 seconds before this code will set. Code 32 — The ECM has detected a problem in the vacuum circuit of the EGR system. For this code to set, the vehicle must be running at 30 mph (48 Km/h) for at least 10 seconds. Code 33 — The absolute pressure circuit (MAP sensor) signal voltage is high. The engine must be run at curb idle for at least 10 seconds before this code will set. Code 51 — Faulty or improperly installed PROM in the ECM. The ignition must be on for approximately 10 seconds before this code will set. Code 52 — A fault within the ECM has been detected. The ignition must be on for approximately 10 seconds before this code will set. Code 53 — The ECM’s 5 volt reference circuit is shorted to ground. The ignition must be on for approximately 10 seconds before this code will set.

| control information label, if present. Should the label be missing, or should the vehicle be equipped with a different engine from the truck’s original equipment, refer to the diagrams below for the same or similar configuration.

EMISSION CONTROLS

TEMPERATURE

SENSOR

AIR CLEANER VACUUM

EMISSION HOSE ROUTING

MOTOR EMISSION HOSE ROUTING PURGE SIGNAL HOSE

ial XA

VAC BRK TVS

4-31

FRONT OF >

ENGINE

7 faa) “4 € VACUUM MOTOR AIR CLEANER

PURGE HOSE

CANISTER

PURGE SIGNAL HOSE

PURGE HOSE

TO CLEAN AIR SUPPLY

O DECELERATION VALVE

FRONT OF

ENGINE

4.1L (LE3) FEDERAL 08F2A MANUAL TRANSMISSION

4.1L (LE3) FEDERAL 08F2A MANUAL TRANSMISSION

8577470b

85774070

Fig. 47 Vacuum hose schematic-1980

Fig. 49 Vacuum hose schematic-1980

VACUUM MOTOR

TEMPERATURE SENSOR

FRONT OF ENGINE

EMISSION HOSE ROUTING

VACUUM MOTOR [EMISSION HOSE ROUTING TEMPERATURE SENSOR TO FUEL TANK CANISTER

[PURGE SIGNAL HOSE

PURGE SIG HOSE TRANSMISSION |) Lock UP CONV VACUUM SWITCH

TRANSMISSION } LOCK UP CONV VACUUM SWITCH

| }——

"

mg==t) DISTRIBUTOR TVS

DISTRIBUTOR

FRONT OF >

ENGINE

4.1L (LE3) FEDERAL 08F2A AUTOMATIC TRANSMISSION 8577470a

4.1L (LE3) FEDERAL 08F2A AUTOMATIC TRANSMISSION 8577470c

Fig. 48 Vacuum hose schematic-1980

Fig. 50 Vacuum hose schematic-1980

4-32

EMISSION CONTROLS

[DS] EMISSION HOSE ROUTING

PURGE SIGNAL HOSE

AIR CLEANER

EMISSION HOSE ROUTING TO FUEL TANK

PURGE SIGNAL HOSE

FRONT OF @>

PURGE HOSE EGR VALVE

——>_ ate

ENGINE

CANISTER

CANISTER

TO FUEL TANK(S)

\£ VAC BRK TVS

ha

CAP

TEMPERATURE SENSOR AIR CLEANER TO CLEAN AIR SUPPLY

DISTRIBUTOR DELAY VALVE

FRONT OF >

O) DECELERATION VALVE

ENGINE

4.1L (LE3) CALIFORNIA 08F2A MANUAL/AUTOMATIC

5.0L (LG9) FEDERAL 08Y2A MANUAL TRANSMISSION 85774071

|

8577471b

Fig. 53 Vacuum hose schematic-1980

Fig. 51 Vacuum hose schematic-1980

PURGE SIGNAL HOSE

EMISSION HOSE ROUTING

oT,

EGR VALVE

TEMPERATURE

SENSOR PURGE

HOSE

CANISTER

AIRCLEANER

VAC

MOTOR}

MANIF VAC SOURCE TO CLEAN

| 2= DISTRIBUTOR TVS

AIR SUPPLY

DELAY VALVE

DISTRIBUTOR gS DECELERATION VALVE

FRONT OF ENGINE » FRONT OF ENGINE

DISTRIBUTOR DELAY VALVE

5.0L (LG9) FEDERAL 08Y2A MANUAL TRANSMISSION

4.1L (LE3) CALIFORNIA 08F2A MANUAL/AUTOMATIC

8577471¢

8577471a

Fig. 52 Vacuum hose schematic-1980

Fig. 54 Vacuum hose schematic-1980

EMISSION CONTROLS

AIR CLEANER VAC TO TEMPERATURE

SENSOR

4-33

[EMISSION HOSE ROUTING

PURGE HOSE

FUEL

AIR CLEANER FRONT OF & ENGINE CANISTER

[EMISSION HOSE ROUTING

DISTRIBUTOR

TRANSMISSION

LOCK UP CONV

DISTRIBUTOR

FRONT OF ENGINE

;

DELAY VACYE

(DISTRIBUTOR

DELAY VALVE

VACUUM SWITCH

TRANSMISSION

LOCK UP CONV

VACUUM SWITCH

5.0L (LG9) FEDERAL 08Y2A AUTOMATIC TRANSMISSION

5.0L (LG9) FEDERAL 08Y2A AUTOMATIC TRANSMISSION 85774072

Fig. 55 Vacuum hose schematic-1980

VN

8577472b

Fig. 57 Vacuum hose schematic-1980

DU

[EMISSION HOSE ROUTING

EMISSION HOSE ROUTING

AIR CLEANER

DISTRIBUTOR DELAY VALVE

heel 3»

5.0L (LG9) FEDERAL 08Y2A MANUAL TRANSMISSION

DISTRIBUTOR DELAY VALVE

ENGINE

5.7 (LS9) FEDERAL 08K4G MANUAL TRANSMISSION 8577472a

Fig. 56 Vacuum hose schematic-1980

FRONT OF

8577472c

Fig. 58 Vacuum hose schematic-1980

4-34

EMISSION CONTROLS

EMISSION HOSE ROUTING

EMISSION HOSE ROUTING

|

PURGE HOSE

PURGE HOSE

PURGE

CANISTER

»

CANISTER

TEMPERATURE SENSOR EFE TVS

AIR CLEANER

CHECK VALVE

DISTRIBUTOR DELAY VALVE

LOCK UP DISTRIBUTOR DELAY VALVE || cony

FRONT OF ENGINE

VACUUM SWITCH

ENGINE

5.7L (LS9) FEDERAL 08K4G AUTOMATIC TRANSMISSION

5.7L (LS9) FEDERAL 08K4G MANUAL TRANSMISSION 85774073

8577473b

Fig. 61 Vacuum hose schematic-1980

Fig. 59 Vacuum hose schematic-1980

EMISSION HOSE ROUTING

EMISSION HOSE ROUTING

TEMPERATURE SENSOR AIR CLEANER

TEMPERATURE SENSOR

Qe

MANIF

svac

Sy, SOURCE

CHECK VALVE pigs "ih

A iy CHECK VALVE

foun ee \

eet

vem

TVS" TRANSMISSION LOCK UP CONV VACUUM SWITCH

DISTRIBUTOR DELAY VALVE FRONT OF ENGINE

5.7L (LS9) FEDERAL 08K4G AUTOMATIC TRANSMISSION

6.6L (LF4) FEDERAL 08K4G AUTOMATIC TRANSMISSION 8577473a

Fig. 60 Vacuum hose schematic-1980

FRONT OF ENGINE 8577473c

Fig. 62 Vacuum hose schematic-1980

EMISSION CONTROLS

VF

EMISSION HOSE ROUTING

4-35

EMISSION HOSE ROUTING

TO FUEL TEMPERATURE

PURGE HOSE

TEMPERATURE SENSOR

SENSOR

TESTER EFE TVS CHECK VALVE

DISTRIBUTOR | TRANSMISSION LOCK UP CONV VACUUM SWITCH

FRONT OF > ENGINE

FRONT OF >

ENGINE

5.7L (LS9) FEDERAL 08K4AA MANUAL TRANSMISSION 85774074

5.7 (LS9) FEDERAL 084KAA AUTOMATIC TRANSMISSION 8577474b

Fig. 63 Vacuum hose schematic-1980

[LH]

CANISTER

Fig. 65 Vacuum hose schematic-1980

EMISSION HOSE ROUTING

EMISSION HOSE ROUTING

[VJ]

PURGE HOSE

PURGE HOSE PURGE HOSE PURGE HOSE

AIR CLEANER

PCV MANIF VAC SOURCE

MOTOR

EMISSION HOSE ROUTING TEMPERATURE SENSOR

§

ge:

O=—

ENGINE

Hove

led ta

DVTR VALVE

AIR PUMP

CARB

THROTTLE RETURN CONTROL VALVE

a

MANIF VAC SOURCE

DISTR Tvs

MANIF VAC SOURCE DISTRIBUTOR DELAY VALVE

FRONT OF & ENGINE

5.7L (LS9) FEDERAL 08K4AA MANUAL TRANSMISSION

4.8L (L25) FEDERAL GM112 MANUAL/AUTOMATIC 85774077

Fig. 76 Vacuum hose schematic-1980

85774078

Fig. 78 Vacuum hose schematic-1980

EMISSION CONTROLS

EMISSION HOSE ROUTING VACUUM

PURGE HOSE

[EMISSION HOSE ROUTING |

CANISTER

PURGE SIGNAL HOSE

4-39

PURGE HOSE

MOTOR

THROTTLE LEVER ACTUATOR

THROTTLE RETURN CONTROL VALVE MANIF VAC SOURCE

FRONT OF ENGINE

U

TEMPERATURE SENSOR

FRONT OF H ENGINE

THROTTLE LEVER ACTUATOR

DISTR

TvS

OS

DELAY VALVE

MANIF VAC

SOURCE

CLEANER

4.8L (L25) FEDERAL GM112 MANUAL/AUTOMATIC

VAC MOTOR

SECONDARY

VACUUM BREAK

® WHERE EQUIPPED

pyr VALVE

5.7 (LT9) CALIFORNIA GM113 MANUAL/AUTOMATIC 8577478a

Fig. 81 Vacuum hose schematic-1980

ig. 79 Vacuum hose schematic-1980

WD

8577478c

EMISSION HOSE ROUTING

TRC SOL

WH]

LEMISSION HOSE ROUTING ]

TRC SOL CONT VALVE

CONT VALVE

FRONT OF >

FRONT OF ®

ENGINE

ENGINE

DISTRIBUTOR

VAC DELAY VALVE

SECONDARY VACUUM BREAK

SECONDARY VACUUM BREAK DVTR VALVE

AIR CLEANER

® WHERE

EQUIPPED

DVTR VALVE

AIR CLEANER

# WHERE EQUIPPED

6.6L (LE4) FEDERAL GM113 AUTOMATIC TRANSMISSION

5.7 (LT9) FEDERAL GM113 MANUAVAUTOMATIC

85774079

8577478b

Fig. 80 Vacuum hose schematic-1980

Fig. 82 Vacuum hose schematic-1980

EMISSION CONTROLS

4-40

PURGE SIGNAL HOSE

EMISSION HOSE ROUTING

PURGE HOSE

EMISSION HOSE ROUTING | PURGE SIGNAL HOSE

PURGE HOSE

XY]

TRC THROTTLE LEVER ACTUATOR

CANISTER LEVER ACTUATOR

CHECK VALVE

FRONT OF @

e

ENGINE

FRONT OF &>

ENGINE

CLEANER

SECONDARY ACN CLOR VACUUM BREAK @ WHERE EQUIPPED

7:4L (LE8) CALIFORNIA GM115 MANUAL/AUTOMATIC

6.6L (LE4) CALIFORNIA GM113 AUTOMATIC TRANSMISSION

8577479¢

8577479a

Fig. 85

Fig. 83 Vacuum hose schematic-1980

EMISSION HOSE ROUTING xX M

| THROTTLE oe

TRC SOL CONT VALVE

=

Vacuum hose schematic-1980

EMISSION HOSE ROUTING

XS

VACUUM

MOTOR

FRONT OF >

AIR CLEANER

ENGINE

I,

THROTTLE LEVER ACTUATOR TE MPERATURE SENSOR

VALVE

AIR PUMP

CARB

THROTTLE RETURN CONTROL VALVE

TEMPERATURE SENET

‘

MANIF VAC SOURCE

FRONT OF >

ENGINE

MANIF VAC SOURCE

}

‘

= DELAY VALVE

4.8L (L25) FEDERAL GM112 MANUAL/AUTOMATIC

7.4L (LE8) CALIFORNIA GM115 MANUAL/AUTOMATIC

85774080

8577479b

Fig. 84 Vacuum hose schematic-1980

DISTR Tvs

Vacuum hose schematic-1980

EMISSION CONTROLS

4-41

FAST IDLE SWITCH EMISSION HOSE ROUTING

Wk’

THROTTLE LEVER

FRONT OF ®>

ACTUATOR

TRC SOL

o{]

CONT VALVE

ENGINE

DISTRIBUTOR VAC DELAY VALVE

SECONDARY VACUUM BREAK

JJ DVTR VALVE

AIR CLEANER

JK

)

TIMING MARKS

# WHERE EQUIPPED

Ss

ee

5.7 (LT9) FEDERAL GM113 MANUAL/AUTOMATIC 8577480a

9.7 (LF9) FEDERAL 09/92 AUTOMATIC TRANSMISSION 8577480¢

Fig. 87 Vacuum hose schematic-1980

EMISSION HOSE ROUTING

wM FRONT OF ENGINE

Fig. 89 Vacuum hose schematic-1980

THROTTLE

TRC SOL

LEVER ACTUATOR @]

CONT VALVE

LABEL CODE ENGINE SIZE EXHAUST EMISSION FAMILY EVAPORATIVE EMISSION FAMILY ADJUSTMENT PROCEDURE

ENGINE ADJUSTMENT SPECIFICATIONS €u19310N HOSE ROOTING

DISTRIBUTOR VAC DELAY VALVE

pin

SECONDARY VACUUM BREAK

gze

aBbea]

DVTR VALVE BEL PART NUMBER

AIRCLEANER

MOTOR

#® WHERE EQUIPPED

EMISSION COMPONENT AND VACUUM HOSE SCHEMATIC

85774081

6.6L (LT9) FEDERAL GM113 AUTOMATIC TRANSMISSION 8577480b

Fig. 90 The Vehicle Emission Control Information label,

Fig. 88 Vacuum hose schematic-1980

located under the hood shows the vacuum hose schematic on 1981 and later vehicles

EMISSION CONTROLS

4-42

DECELERATION VALVE

TEMPERATURE SENSOR

TEMPERATURE SENSOR

@

a 5S

TO CLEAN AIR SUPPLY

SPARK RETARD DELAY VALVE

PURGE HOSE

i

DVTR VALVE

PURGE SIGNAL HOSE

AIR PUMP

SPARK RETARD DELAY VALVE DISTRIBUTOR TVS

PURGE HOSE

TO FUEL TANK VENT CAP

—#—

PURGE SIGNAL HOSE

CANISTER

“e

CANISTER PURGE TVS CANISTER

CANISTER PURGE TVS

8577412a

8577410a

Fig. 91 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

Fig. 93 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

and low altitude with manual transmission

and low altitude with manual transmission alternate

DECELERATION VALVE

LOL)

Bs | |

ne,

{|

TO CLEAN AIR SUPPLY PURGE HOSE

DISTRIBUTOR

as] rg

SPARK RETARD DELAY VALVE

en.

FF

CANISTER PURGE TVS)

hsec

ESR

MANIF~ RESTRE@GR tui VAC SRC £4 hh.

PURGE SIGNAL HOSE

| TO FUEL TANK

TO FUEL TANK VENT CAP

DISTRIBUTOR TVS

SPARK RETARD DELAY VALVE

TEMPERATURE SENSOR

AUXILLIARY

CANISTER

9)

VENT CAP

PURGE SIGNAL HOSE CANISTER PURGE TVS

CANISTER: 8577411la

8577413a

Fig. 92 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

Fig. 94 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

and low altitude with manual transmission alternate

and low altitude with manual transmission alternate

EMISSION CONTROLS

XCD

DECELERATION

=

VALVE

EGR BLEED

4-43

XCH

y§ MALES

SOLENOID

C2) Om

TVS

EGR BLEED SOLENOID

SENSOR

an

VA

SPARK RETARD DELAY VALVE

VEHICLE

Sd

DISTRIBUTOR DVTR VALVE AIR PUMP

PURGE SIGNAL HOSE

P, SPARK RETARD DELAY VALVE

TO FUEL TANK

DISTRIBUTOR AND CANISTER PURGE TVS

=

TRANS TORQUE CONV CLUTCH TVS TRANS CONV VACUUM

TRANS TORQUE

anil

DELAY VALVE

SWITCH

CANISTER

DISTRAND CAN

CONV CLUTCH

PURGE TVS

Vs

8577414a

DELAY VALVE

TRANS CONV

&/ vacuum switcH

8577416a

Fig. 95 1984 250 (4.1L) 6-cylinder engine — 2bbi federal

Fig. 97 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

and low altitude with automatic transmission

and low altitude with automatic transmission alternate

DECELERATION VALVE

oo Ys

EGR BLEED

O

SOLENOID

Q

VAC BRK

|

Ape Tvs

TEMP SENSOR

PURGE HOSE e DISTRIBUTOR

SPARK RETARD DELAY VALVE DISTRIBUTOR AND CANISTER PURGE TVS

le

—————

Ae a>

6.O

-

;

AUX CANISTER

EGR BLEED SOLENOID TEMP SENSOR

SPARK RETARD DELAY VALVE

‘

VEHICLE

DISTRIBUTOR

PURGE SIGNAL

HOSE TO FUEL TANK

TO FUEL TANK VENT CAP

AUXILLIARY ©) TER CANISTE

85774105

CANISTER’

LA DISTRANDCAN pURGE TVS

‘DELAY VALVE

TRANS TORQUE $F TRANS CONV CONV CLUTCH Y Pe

VACUUM SWITCH 85774107

Fig. 96 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

Fig. 98 1984 250 (4.1L) 6-cylinder engine — 2bbl federal

and low altitude with automatic transmission alternate

and low altitude with automatic transmission alternate

DECELERATION VALVE

Mt ..

Lb ASAEVAC BRK

(LI

AND EGR S

ww

TEMP

C\-. VACUUM

SENSOR

OS MOTOR

SENSOR S,

Mer(sec

—_ Hi

Ho, VAC BRK RAOER

ee

BE

le TEae ae |

DISTRIBUTOR AND CANISTER PURGE TVS

:

AL neuaets

SPARK RETARD DELAY VALVE

VEHICLE

PURGE HOSE

ts

SPARK RETARD DELAY VALVE

5)

7

es

PE-DVTR VLV 4

_

PURGE SIGNAL

DISTRIBUTOR

HOSE

TO FUEL TANK

AIR PU

TO FUEL TANK

i

aS

CANISTE

—-_ DISTR AND CAN PURGE TVS

TRANS TORQUE CONV CLUTCH TvS

DELAY VALVE TRANS CONV y

VACUUM SWITCH 85774110

85774108

Fig. 101 1984 250 (4.1L) 6-cylinder engine — 2bbl

Fig. 99 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and low altitude with automatic transmission alternate

DECELERATION VALVE

federal and low altitude with automatic transmission alternate

—

DECELERATION VALVE

| —

:

Ge G/

SK

VAC BRK ] AND

8 Tvs

EGR

TEMPERATURE SENSOR

TEMP SENSOR

/¥)

EGR

@: PHD 6 OG

BE

ties

Gis

SPARK RETARD DELAY VALVE

:

AIR PUMP fl

='

PURGE HOSE AUX CANISTER PURGE SIGNAL

SPARK RETARD DELAY VALVE

DISTRIBUTOR

HOSE

TO FUEL TANK

DISTRIBUTOR AND CANISTER PURGE TVS

VEHICLE

DVTRVLV AIR PUMP

TO FUEL TANK VENT CAP AUXILLIARY (6) CANISTER CANISTER

ea) =TRANS TORQUE DISTR AND CAN CONV CLUTCH PURGE TVS Tvs

@

DELAY VALVE TRANS CONV VACUUM SWITCH

85774111

85774109

Fig. 100 1984 250 (4.1L) 6-cylinder engine — 2bbI

Fig. 102 1984 250 (4.1L) 6-cylinder engine — 2bbl

federal and low altitude with automatic transmission alternate

federal and low altitude with automatic transmission alternate

EMISSION CONTROLS

XCK

DECELERATION VALVE

el ee)

4-45

DECELERATION VALVE

VAC BRK AND EGR

[rvs yw

5

VACUUM MOTOR

TEMPERATURE

TEMPERATURE SENSOR

TO CLEAN AIR SUPPLY

VACUUM MOTOR

SPARK RETARD DELAY VALVE

DVTR VLV PURGE SIGNAL HOSE

AIR PUMP

SPARK RETARD

DELAY VALVE

DISTRIBUTOR TVS

FRONT

) VEHICLE

PURGE HOSE

TO FUEL TANK

VENT CAP

CANISTER PURGE TVS

CANISTER PURGE TVS

85774114

85774112

Fig. 105 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and high altitude with manual transmission alternate

Fig. 103 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and high altitude with manual transmission

DECELERATION VALVE

=== Cg:

:

LS /

TEMPERATURE SENSOR

p

VAC BRK

AND EGR

[S }tvs

Ze

|

TEMPERATURE SENSOR

VAC,

(erk[

TO CLEAN AIR SUPPLY

wo.)H

bs

PURGE HOSE

PURGE HOSE

ISTRIBUTOR PURGE SIGNAL

i

SPARK RETARD DELAY VALVE

SPARK RETARD DELAY VALVE

A

ez] eal '

A

CANISTER

TRANS CONV VACUUM SWITCH

PURGE SIGNAL

[ fair pump dl| q HOSE

eens DISTRIBUTOR AND i I CANISTER PURGE TVS 5 _5 = TRANS TORQUE CONV CLUTCH TVS

DISTRIBUTOR TVS CANISTER PURGE Tvs » AUXILLIARY CANISTER

|

af ' Pe DVTR VLVG

a

TO FUEL TANK

“CIVALVE

85774113

Fig. 104 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and high altitude with manual transmission alternate

85774115

Fig. 106 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and high altitude with manual transmission alternate

VACUUM BREAK AND EGR TVS

DIFFERENTIAL PRESSURE SENSOR

MANIFOLD VACUUM SOURCE

On

SECONDARY VAC SOURCE

VACUUM MOTOR VEHICLE

@

SPARK RETARD

DELAY VALVE

s

MANIFOLD VACUUM SOURCE

al

E TT)

(7

DECELERATION VALVE

TIfF OVTR

DISTRIBUTOR

VLV AIR PUMP PURGE HOSE

3

TO FUEL TANK VENT CAP

DISTRANDCAN CANISTER * puRGE TVS

TRANS TORQUE

CONV CLUTCH Tvs

AIR MANIFOLD VALVE

DELAY VALVE

DISTRIBUTOR 3

TRANS CONV VACUUM SWITCH

Bi) 6

CANISTER

|} PURGE HOSE

MY

PURGE TVS AIR PUMP

CANISTER 85774126

85774124

Fig. 115 1984 250 (4.1L) 6-cylinder engine — 2bbI federal and high altitude with automatic transmission alternate

Fig. 117 1984 250 (4.1L) 6-cylinder engine — 2bbl federal and high altitude with automatic transmission alternate

xCZ VACUUM BREAK AND EGR TVS

MANIFOLD

DIFFERENTIAL PRESSURE SENSOR

VACUUM

BREAK AND EGR TVS

SECONDARY VAC BRK

TEMPERATURE SENSOR

VACUUM MOTOR

ace

cane

DECELERATION VALVE

DISTRIBUTOR

VENT CAP AUXILIIARY 6)

VEHICLE

DISTRIBUTOR 3)

TO FUEL TANK

oY

CANISTER CANISTER“

-_

DISTR AND CAN PURGE TVS

TRANS TORQUE

CONV Tvs

CLUTCH

TO FUEL TANK

DELAY VALVE

TRANS CONV VACUUM SWITCH

AIR MANIFOLD VALVE

VENT CAP

AIR PUMP

85774125 85774127

Fig. 116 1984 250 (4.1L) 6-cylinder engine — 2bbI federal and high altitude with manual transmission alternate

| Fig. 118 1984 250 (4.1L) 6-cylinder engine — 2bbl California and low altitude with manual transmission

EMISSION CONTROLS

xcy

VACUUM

EGR BLEED SOLENOID wanirorp

BREAK AND EGR TVS MANIFOLD VACUUM SOURCE SECONDARY VAC BRK

DIFFERENTIAL PRESSURE SENSOR

DIFFERENTIAL

VACUUM

MANIFOLD VACUUM SOURCE

B

: (i

Le ee

72

RB

a

=

VEHICLE

aC

2p jh DECELERATION

» /| ee

TO FUELTANK

|:

ee

PURGE HOSE

A ND

D

CANISTER PURGE TVS

Se.

bf

AIR MANIFOLD VALVE

DISTRIBUTOR ©

:

PRIMARY VAC BRK

SOURCE

DECELERATION VALVE

VACUUM BREAK AND EGR TVS Sa

PRESSURE SENSOR TEMPERATURE SENSOR

MANIFOLD VACUUM

4-49

g AUX

PURGE SIGNAL HOSE

' VEHICLE

CANISTER

CANISTER

AIR PUMP

85774128

85774130

Fig. 119 1984 250 (4.1L) 6-cylinder engine — 2bbl

Fig. 121 1984 250 (4.1L) 6-cylinder engine — 2bbl

California and low altitude with manual transmission alternate

California and low altitude with manual transmission alternate

XDA

MANIFOLD VACUUM SOURCE

G

VACUUM BREAK AND EGR TVS

XDC

SECONDARY VAC BRK

DIFFERENTIAL PRESSURE SENSOR

7

a

DIFFERENTIAL PRESSURE SENSOR

B

EGR BLEED SOLENOID

VACUUM BREAK AND EGR TVS —— ; MANIFOLD VACUUM SOURCE

TEMPERATURE SENSOR

PRIMARY VAC BRK

-

.

TEMPERATURE SENSOR VAC MOTOR

MANIFOLD VACUUM SOURCE MANIFOLD VACUUM

SOURCE

VEHICLE

DECELERATION VALVE

DECELERATION VALVE

TO FUEL TANK

DISTRIBUTION i) TO FUEL TANK

ADP

VENT CAP

DISTRIBUTOR 4)

AUXILLIARY CANISTER 85774129

Fig. 120 1984 250 (4.1L) 6-cylinder engine — 2bbl California and low altitude with manual transmission alternate

RESTR

CANISTER PURGE TVS |_| hee AIR PUMP

ra

A

urce Hose f

UCTS) PURGE SIGNAL HOSE ANEEE

CANISTER 85774131

Fig. 122 1984 250 (4.1L) 6-cylinder engine — 2bbl California and low altitude with automatic transmission

EGR BLEED

|XDD}

SOLENOID

DIFFERENTIAL PRESSURE SENSOR

MANIFOLD VACUUM

;

SOURCE

SECONDARY VAC BREAK SENSOR

DISTRIBUTOR oe)

PURGE HOSE

:

EGR BLEED

Wy

Rl

eke

B S}

DISTRIBUTOR DELAY VALVE

(¢

tc S00

oo“

MANIFOLD VACUUM SOURCE

:

SOLENOID

TE BES

|(SRE

DECELERATION VALVE

TO FUEL TANK

y)

wy

a

MANIFOLD VACUUM SOURCE

VACUUM

(4

1

VENT CAP

AIR PUMP

CANISTER

:

| DECELERATION ——

—{((—©4

EGR/PURGE/TCC TVS

PURGE SIGNAL HOSE

PURGE SIGNAL HOSE TRANS CONV VACUUM SWITCH

85774132

Fig. 123 1984 250 (4.1L) 6-cylinder engine — 2bbl California and low altitude with automatic transmission alternate

85774134

Fig. 125 1984 305 (5.0L) V8 engine — 4bbl federal and | low altitude with automatic transmission

s

EGR BLEED SOLENOID

[XOF|

VACUUM

MANIFOLD

SECONDAR

4

PRESSURE

SENSOR

ee

BREAK AND EGR

TVS

f

DIFFERENTIAL

Y

y

eS a

4

) )

EGR BLEED SOLENOID

TEMPERATURE SENSOR 4

(ia)

TEMPERATURE

AIR CLEANER

SENSOR

VACUUM MOTOR

MANIFOLD VACUUM SOURCE |

=

A

ees

DECELERATION VALVE

:

Y

ae

:

MACOUM MOTOR

DISTRIBUTOR DELAY VALVE

DECELERATION

VALVE

PCV VALVE

VEHICLE

e

cS

:

E

TO FUEL TANK VENT CAP AUXILLIARY @) CANISTER

CANISTER

‘ i

“7 PURGE Ws

SIGNAL HOSE

VEHICLE

5

: .

DELAY VALVE

CANISTER 85774133 85774135

Fig. 124 1984 250 (4.1L) 6-cylinder engine — 2bbl California and iow altitude with automatic transmission alternate

Fig. 126 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with automatic transmission alternate

Lo.

EMISSION CONTROLS

TIP IN VACUUM SWITCH

1 aX)

t.

CZ;

ane

S

q)) 5,

ey

J

MANIFOLD

vacuum & SOURCE

te

4-51

TEMPERATURE SENSOR AIR CLEANER A-

VACUUM MOTOR DECELERATION VALVE

|CARBURETOR PCV VALVE

PCV VALVE EGR BLEED SOLENOID

DELAY VALVE

AIR PUMP. VEHICLE

EGR/PURGE/TCC TVS

TRANS CONV VACUUM SWITCH 85774138

85774136

Fig. 127 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with automatic transmission alternate

XDM

Fig. 129 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

DISTRIBUTOR TVS

TIP IN VACUUM SWITCH

CARBURETOR PCV VALVE

VEHICLE

DVTR VALVE AIR PUMP

EGR/PURGE/TCC TVS

\? 7 TRANS CONV DECELERATION TI VACUUM SWITCH

85774137

Fig. 128 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission

EGR/PURGE TVS

PURGE SIGNAL HOSE 85774139

Fig. 130 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with manual transmission —

4-52

EMISSION CONTROLS

(y~

TEMP SENSOR

, oe

mxy

AIR CLEANER

O (EGR

: _vacuumsourRce

VACUUM MOTOR

|

VAC R-MANIF VAC woroR SOURCE

DECELERATION DVTR VALVE

z

VEHICLE

VALVE

N ‘

PCV VALVE

PURGE HOSE

Sie

TO FUEL TANK ' '

' q

uy

SY

8) CANISTER

VEHICLE

+

AIR PUMP 85774140

Fig. 131 1984 305 (5.0L) V8 engine — 4bbli federal and high altitude with manual transmission alternate

(y~

85774142

Fig. 133 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with manual transmission alternate

)~TEMP SENSOR

TEMPERATURE SENSOR AIR CLEANER VACUUM MOTOR

MANIFOLD VACUUM SOURCE

(})EGR

Q

vac

“MANIF VAC ywotoR SOURCE

Fenner{OT

SIGNAL HOSE

EGR/PURGE TVS

SIGNAL HOSE

85774141

Fig. 132 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with manual transmission

85774143

Fig. 134 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with manual transmission alternate

EMISSION CONTROLS

[XZ]

con aveeo

4-53

DISTRIBUTOR Tvs

DISTRIBUTOR

SOLENOID

TEMPERATURE SENSOR

VACUUM MOTOR DECELERATION VALVE

PCV VALVE

PURGE SIGNAL HOSE PURGE HOSE TO FUEL TANK CANISTER

CANISTER

85774144

Fig. 135 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with manual transmission alternate

85774146

Fig. 137 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

Cy-

TEMP SENSOR

Pe

\) AIR CLEANER

CANISTER

PURGE SIGNAL HOSE

DW } Decet valve

PURGE HOSE

85774147

85774145

Fig. 136 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

SIGNAL

EGR/PURGE TVS

Fig. 138 1984 305 (5.0L) V8 engine — 4bbl federal and low altitude with automatic transmission alternate

4-54

EMISSION CONTROLS

EGR BLEED SOLENOID

()-TEMP SENSOR

K

TEMP SENSOR

’ AIR CLEANER

DECEL VALVE PCV VALVE

aS

PURGE HOSE

SIGNAL 85774150

85774148

Fig. 139 1984 305 (5.0L) V8 engine — 4bbl federal and

Fig. 141 1984 305 (5.0L) V8 engine — 4bbli federal and

low altitude with automatic transmission alternate

low altitude with automatic transmission alternate

TEMP SENSOR

TEMP SENSOR

AIR CLEANER

AIR CLEANER

SOURCE

Y)

VAC MOTOR

DECEL VALVE

PCV VALVE EGR BLEED SOLENOID PURGE HOSE TO FUEL TANK

EGR/PURGE TVS

PURGE SIGNAL HOSE 85774149

Fig. 140 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

85774152

Fig. 142 1984 305 (5.0L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

EMISSION CONTROLS

&39

DISTR DELAY =)

oa—_DIstR VALVE

Yy

)

4-55

TEMP SENSOR AIR CLEANER

EGR BLEED SOLENOID

SOLENOID

5

VEHICLE Sd PURGE HOSE

Yuss:

DISTR DELAY

RESTR

zig\2

:

TO FUEL TANK

DVTR VLV

H Lave EGRIPURGE/ o>

PURGE SIGNAL HOSE puRGE SIGNAL HOSE 85774151

85774154 |

Fig. 143 1984 350 (5.7L) V8 engine — 4bbl federal and low altitude with automatic transmission

EGR BLEED

ax 2S

oe

TEMP SENSOR

TR

AIR CLEANER

DECEL VALVE

PCV VALVE

Fig. 145 1984 350 (5.7L) V8 engine — 4bbl federal and high altitude with automatic transmission

DISTR

‘bg

DISTR DELAY VLV

’

DISTR Tvs Bead

—J

TEMP SENSOR

AIR CLEANER

DECEL VALVE PCV VALVE

PURGE HOSE, TO FUEL TANK

PEAY Fl VEHICLE

ALVE

CANISTER

PY TRANS CONV VAC SW 85774153

Fig. 144 1984 350 (5.7L) V8 engine — 4bbl federal and low altitude with automatic transmission alternate

TRANS CONV VAC SW 85774155

Fig. 146 1984 350 (5.7L) V8 engine — 4bbl federal and high altitude with automatic transmission alternate

4-56

EMISSION CONTROLS

TEMP SENSOR

* DIFF PR CJ seNsoR L } DISTRIBUTOR

XFJ

O MANIFOLD VACUUM SOURCE TO FUEL TANK

VEHICLE ; @&

PURGE HOSE

PURGE HOSE TO FUEL TANK

CANISTER AIR MANIFOLD VALVE

PURGE SIGNAL HOSE

PURGE SIGNAL HOSE

AIR PUMP

85774158

85774156

Fig. 147 1984 350 (5.7L) V8 engine — 4bbl federal and

Fig. 149 1984 350 (5.7L) V8 engine — 4bbi California

low altitude with manual transmission

and low altitude with automatic transmission

Int

VEHICLE

e

ay)

PURGE HOSE

CQ) MANIFOLD VACUUM SOURCE TO FUEL TANK

PURGE HOSE

ENGINE

e AIR MANIFOLD VALVE AIR PUMP.

85774157

Fig. 148 1984 350 (5.7L) V8 engine — 4bbl federal and high altitude with manual transmission

PURGE SIGNAL HOSE

85774159

Fig. 150 1984 350 (5.7L) V8 engine — 4bbl California and low altitude with automatic transmission alternate

EMISSION CONTROLS = 4-57

TEMP

VACUUM BREAK “2

SeNson

Ag

4sigs

ee

UDY (DISTRIBUTOR

ASI vac on O1STR

MANIFOLD VACUUM

O source

()

SECONDARY DECELERATION VALVE

PCV VALVE AIR MANIFOLD VALVE

Nt

PURGE HOSE

As

ee

i

| aoa

PURGE SIGNAL HOSE

CANISTER

ELECT PURGE SOLENOID

AIR PUMP

FRONT

* 85774160

oe

VEHICLE

A) rh CONAEC TOR 8,

WEN

USED

pue

eae wien?

EMISSION

HOSE

to FUEL

ROUTING

CNSTR

TANK

85774162

Fig. 151 1984 350 (5.7L) V8 engine — 4bbl California and low altitude with automatic transmission alternate

—

a

Fig. 153 1985 260 (4.3L) V6 engine — 4bbl federal and low altitude with automatic (A4) transmission

VEHICLE PURGE SIGNAL @

P—JPELECT PURGE SOLENOID 85774161

FRONT o VEHICLE SPARK

OF LAY

EMISSION HOSE ROUTING

RETARD

VLV