Chevrolet 70 1969 Series, Shop Manual

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G ASO LINE ENGINES 6A-19
LACK OF POWER (CONT.)
S Y M P T O M D - F A U L T Y A C C E L E R A T IO N
POSSIBLE CAUSES
1. Defective carburetor (accelerator pump
clogged jets).
2. Defective governor.
3. Air leak at intake manifold.
4. Faulty ignition wiring.
5. Misfiring spark plugs.
6. Lack of cylinder compression, due to worn
piston rings, burned valves, or defective head
gasket.
7. Exhaust back pressure too high.
R E M E D Y
1. Repair or replace carburetor.
2. Repair or replace governor.
3. Replace gaskets and/or manifold.
4. Inspect for excessive resistance and defective
insulation.
5. Clean and/or replace sparkplugs.
Replace defective parts or, overhaul engine.
Replace or repair defective exhaust system
components.
OVERHEATING
POSSIBLE CAUSES
1. Loose or defective fan belt.
2. Thermostat(s) not opening.
3. Coolant loss.
4. Partially clogged radiator.
5. Defective water pump.
6. Incorrect ignition or valve timing.
7. Dragging brakes.
8. Restricted exhaust system.
9. Improper valve clearances.
10. Ignition distributor advance inoperative.
11. Overloaded vehicle.
R E M E D Y
1. Adjust or replace belt.
2. Replace thermostat.
3. Check for leaks and repair as necessary.
4. Clean radiator core internal passages, and
air passages.
5. Repair or replace pump.
6. Retime engine.
7. Adjust or repair brakes.
8. Clean or replace exhaust system components.
9. Adjust valve clearance.
10. Repair distributor to correct malfunction.
11. Reduce load per vehicle rating.
N O T E : When operating vehicle in hot climate or at high altitudes, it may be neces­
sary to check pressure cap and/or use cap with higher opening pressure to prevent
boiling.
ROUGH IDLE A N D /O R STALLING
S Y M P T O M A - ER R A T IC RU N N IN G O R SURGING
POSSIBLE CAUSES
1. Idle mixture too rich.
2. Improper ignition timing.
3. Vacuum leak (air entering intake manifold).
R E M E D Y
1. Adjust idle mixture screws.
2. Set timing.
3. Replace gasket, or tighten manifold bolts. Check
and/or replace vacuum brake hose (when used).
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHOP M ANUAL