Tune-Up - 5.0l v8 VIN [h] GMC Vandura I

ENGINE IDENTIFICATION

Engines can be identified by eighth digit of Vehicle Identification Number (VIN). Number is located on plate at top left corner of dashboard and at base of steering column on van models.

Engine code numbers are located at front of block, at right cylinder head.

VIN ENGINE CODES

TUNE-UP NOTES

Note. When performing tune-up procedures described in this article, the following notes and precautions must be observed

Due to changes and corrections, always refer to Engine Tune-Up Decal in engine compartment before attempting tune-up. In the event of a conflict between specifications given in this manual and decal specifications, decal specifications prevail.

When performing tune-up on vehicles equipped with a catalytic converter, do not allow or create a condition of engine misfire in one or more cylinders for an extended period of time. Damage to converter from overheating may occur due to loading with unburned fuel.

ENGINE COMPRESSION

When making compression checks, disconnect the ignition switch connector pink wire from high energy ignition system. With air cleaner removed and throttle and choke wide open, crank engine through at least four compression strokes.

COMPRESSION SPECIFICATIONS

VALVE CLEARANCE

All vehicles are equipped with hydraulic lifters. Lifters should be adjusted to 1 turn down from zero lash.

VALVE ARRANGEMENT

E-I-I-E-E-I-I-E (Both banks, front-to-rear)

FIRING ORDER & DISTRIBUTOR/PICKUP INFORMATION

The Federal emissions 5.0L engine is a high compression (9.2:1) model and uses an Electronic Spark Control (ESC) ignition system with detonation sensor and 5-pin ignition module inside the distributor.

Note. High energy ignition system module must be replaced as a unit. A liberal coat of silicone grease MUST be applied to both the module and the surface on which it will be mounted to prevent thermal overheating.

DISTRIBUTOR PICKUP COIL RESISTANCE

Timing Mark & Firing Order: Timing Socket at 10 Degrees ATDC. Scheme 1

IGNITION TIMING

Note. Engines are equipped with a receptacle for magnetic probe timing lights, located 10° ATDC. DO NOT use this location for timing with a conventional light.

1. Connect an adapter between No. 1 spark plug wire or use an inductive type pickup. DO NOT puncture wires. Connect timing light according to manufacturer's instructions.
2. Check or adjust ignition timing with engine at normal operating temperature with distributor vacuum line disconnected and plugged. (Scheme 1) Models with automatic transmission should be in "D", all others in neutral.

TIMING SPECIFICATIONS

SPARK PLUG SPECIFICATIONS

SPARK PLUG SPECIFICATIONS

SPARK PLUG PART NUMBER

HIGH TENSION WIRE RESISTANCE

Carefully remove ends of wire from spark plug and distributor. Using an ohmmeter, check resistance while gently twisting wire. If resistance is not to specifications, or fluctuates from infinity to any value, replace cable.

RESISTANCE

IGNITION COIL

COIL RESISTANCE

COIL OUTPUT

CARBURETOR APPLICATION

CARBURETORS

FUEL PUMP SPECIFICATIONS

FUEL PUMP SPECIFICATIONS (1)

MIXTURE SCREW PLUG REMOVAL

1. Remove carburetor from engine and drain fuel. Invert carburetor and make 2 parallel cuts in the throttle body on either side of the locator points beneath the idle mixture needle plug (manifold side) with a hacksaw.
2. The cuts should reach down to the steel plug but should not extend more than 1/8" beyond the locator points. The distance between the saw marks depends on the size of the punch to be used.
3. Place a flat punch at a point near the ends of the saw marks in the throttle body. Holding the punch at a 45° angle, drive it into the throttle body until casting breaks away, exposing the steel plug.
4. Holding a center punch vertical, drive it into the steel plug. Holding the punch at a 45° angle, drive out the steel plug.

IDLE MIXTURE CHECK & ADJUST - (PROPANE ENRICHMENT)

1. With engine at normal operating temperature, choke fully open and A/C "OFF" (if equipped), set parking brake and block drive wheels. Disconnect and plug hoses as directed on Emission Control/ Tune-Up decal.
2. Connect tachometer to engine. Disconnect vacuum advance and set timing to specification. Reconnect vacuum advance. Disconnect crankcase ventilation tube from air cleaner.
3. Insert hose with rubber stopper (tool J-26911) from propane valve into PCV tube opening in air cleaner. Propane bottle must be in vertical position.
4. Slowly open control valve until maximum engine speed is reached with transmission in "D" (automatic) or neutral (manual). NOTE: Too much propane will cause engine speed to drop.
5. Observe propane flow meter to ensure propane cartridge is full. With propane flowing, adjust idle speed screw or solenoid so speed rises above normal idle by specified amount.
6. Readjust propane flow to be certain of maximum engine speed and adjust idle speed if necessary. Turn off propane. Run engine at 2000 RPM in neutral for 30 seconds, return to idle, and place in "D".
7. Check idle speed. If correct, no adjustment of mixture is necessary. If not correct, proceed with adjustment procedure. If idle speed is too low, carefully remove caps from mixture screws and back out screws (richen) 1/8 turn at a time until correct speed is reached.
8. If RPM is too high, turn screws in (leaner) 1/8 turn at a time until correct speed is reached. Turn propane on again to check maximum engine idle speed.
9. If RPM does not meet specifications, readjust idle speed screw or solenoid screw to obtain specified enriched RPM with propane flowing.
10. Turn off propane, place transmission in neutral and run engine at 3000 RPM for 30 seconds. Recheck idle speed and repeat procedure if necessary.

PROPANE ENRICHED RPM

AUTOMATIC CHOKE

The choke cover on all models is riveted in place and no adjustments are possible or necessary.

COLD (FAST) IDLE RPM

1. Place transmission in neutral. Move cam follower onto highest step of fast idle cam. Disconnect and plug vacuum hose to EGR valve, canister purge hose and purge signal hose at canister.
2. Start engine without touching throttle. Turn fast idle speed screw to adjust speed to specification.

Note. For information regarding the choke, look at AUTOMATIC CHOKE under FUEL SYSTEMS in this article.

FAST IDLE SPEED

HOT (SLOW) IDLE RPM

On some models, an Idle Speed Solenoid is used to position the primary throttle valve to provide engine idle speed requirements.

HOT IDLE SPEED ADJUSTMENT

Note. See engine compartment Emission Control Tune-Up Decal to prepare engine for idle speed adjustment.

1. Set ignition timing to specifications. Disconnect lead from idle speed solenoid (if equipped). Adjust curb idle speed to specifications using idle speed screw. Transmission should be in "D" if equipped with an automatic transmission, and in neutral for all others.
2. Disconnect lead from air conditioning compressor. Reconnect lead at idle solenoid, then turn air conditioning "ON". Open throttle slightly to allow solenoid to fully extend. Adjust solenoid idle speed by turning solenoid screw.

A/C IDLE SPEED SOLENOID (ISS) ADJUSTMENT

Note. Not all models have an ISS.

1. Prepare vehicle for adjustments according to directions on Emission Label on vehicle. Disconnect solenoid and turn air conditioning off. Set curb idle speed with idle speed screw.
2. Connect solenoid. Disconnect A/C lead at compressor and turn A/C on. Place automatic transmission in "D" and manual transmission in neutral.
3. Open throttle to extend solenoid plunger. Turn solenoid screw to adjust RPM. Reconnect A/C lead.

A/C IDLE SPEED SOLENOID (ISS) FUNCTIONAL CHECK

Note. Not all models have an ISS.

1. Turn on the ignition, but do not start the engine. Turn the A/C to ON position. Open the throttle to allow the solenoid to extend, then close the throttle. Disconnect the lead at the solenoid. The solenoid plunger should drop away from the throttle lever.
2. Connect the solenoid lead. The plunger should move out and contact the throttle lever. The solenoid may not be strong enough to open the throttle, but the plunger should move.
3. If the plunger does not move in and out when the lead is disconnected and connected, insert a test light between the solenoid feed wire and ground. If the light lights, replaced the solenoid. If the light does not light, locate the cause of the open circuit solenoid feed wire.

EMISSION CONTROL

There is no information regarding emissions control in this article. Please see the appropriate article in the EMISSIONS section.

ALTERNATOR

All models are equipped with Delco alternators with integral voltage regulators.

ALTERNATOR SPECIFICATIONS

ALTERNATOR REGULATOR

Regulators are Delco nonadjustable, integral with alternator.

REGULATOR SPECIFICATIONS

BATTERY

BATTERY

STARTER

All models are equipped with Delco overrunning clutch starters.

STARTER SPECIFICATIONS

BASIC SERVICE INTERVALS

REPLACEMENT INTERVALS

FLUID CAPACITIES

FLUID CAPACITIES

BELT ADJUSTMENTS

BELT ADJUSTMENT (1)

See also:
• AUTOMATIC CHOKE