GMC 4000 Series Service Manual page 294

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SYMPTOM A - SLOW CRANKING
POSSIBLE CAUSES
1. Heavy engine oil.
2. Partially discharged battery.
3. Faulty or undercapacity battery.
4. Poor battery connections.
5. Faulty starter solenoid.
6. Faulty starting motor or drive.
SYMPTOM B - LOW CYLINDER COMPRESSION
POSSIBLE CAUSES
1. Burned or warped valves.
2. Improper valve lash.
3. Worn or broken piston rings.
4. Defective cylinder head gasket.
SYMPTOM C - LACK OF FUEL
POSSIBLE CAUSES
1. Fuel lines clogged.
2. Low fuel supply.
3. Clogged vent in fuel tank cap.
4. Break in fuel supply line allowing air to be
drawn into fuel line.
5. Clogged fuel filter.
6. Water or ice in fuel system .
7. Defective fuel pump.
8. Dirty carburetor.
9. Carburetor choke inoperative, or not properly
adjusted.
SYMPTOM D - IGNITION TROUBLES
POSSIBLE CAUSES
1. Distributor points burned or corroded.
2. Distributor points out of adjustment.
3. Faulty spark plugs.
4. Defective wiring.
5. Ignition out of time.
G M C S E R V I C E M A N U A L
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HARD STARTING
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REMEDY
1. Change to lighter oil.
2. Charge battery.
3. Replace battery.
4. Clean and tighten or replace connections.
5. Replace or repair solenoid.
6. Overhaul starting motor.
REMEDY
1. Overhaul cylinder head.
2. Adjust to proper clearance.
3. Overhaul engine.
4. Replace gasket.
REMEDY
1. Clean fuel lines.
2. Check amount of fuel in tank, fill if supply is low.
3. Clean or replace cap.
4. Replace or repair lines.
5. Service filter as recommended in applicable
portion of ENGINE FUEL SYSTEM (SEC. 6M).
6. Thaw if frozen, and drain water out of tank and
filters.
7. Make pressure test at pump outlet.
8. Clean carburetor.
9. Check choke operation and adjust as necessary.
REMEDY
1. Clean or replace points.
2. Adjust point gap.
3. Clean or replace and adjust spark plug gap.
4. Inspect wiring and correct as required.
5. Set ignition timing.
Sec. 6A
Page 283
GASOLINE ENGINES
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