GMC 1976 ZEO 6083 Maintenance Manual page 277

6A- 1 2 ENGINE
ENGINE HESITATES OR STALLS DURING ACCELERATION (1)
(SPITBACK THROUGH CARBURETOR)
GENERAL
IGNITION (2)
Vapor lock . (11)
Carburetor icing. (5)
Restricted exhaust .
Compression low.
Intake manifold leaking (Carburetor at-
taching bolts loose) . (9)
Partly blocked or dragging brake shoes
(Refer to "Brake" chart) .
Air cleaner dirty.
Engine timing.
Excessive carbon in engine .
Heavy oil in engine .
Wrong or poor grade fuel .
Excessive rolling resistance from low air
in tires, applied brakes, wheel alignment,
overloading etc.
GENERAL
Exhaust system restricted or faulty .
Cylinder(s) not firing properly .
T.V .S . switch faulty . (1)
Vacuum leaks. (9)
IGNITION
Check out complete ignition system . (2)
Faulty spark plug wires.
LACK OF POWER OR HIGH SPEED PERFORMANCE
NOTE :
It should be noted that the altitude of operation has a decided effect on
performance. An engine adjusted for normal altitudes will lack performance at
high altitudes, whereas an engine when operating normally at high altitudes may
have a lean carburetor adjustment and show signs of pre-ignition when operated
at sea level.
IGNITION (2)
ENGINE SURGES (1)
Ignition timing or dwell incorrect.
Centrifugal governor advance not operating
properly .
Vacuum advance not operating properly .
Ignition points burned, pitted, sticking,
or bouncing . (Due to weak breaker arm
spring).
Faulty spark plugs.
Faulty ignition cables .
Faulty ignition coil or condenser.
Worn or burned distributor rotor.
Worn distributor shaft or cam.
Poor ground .
Distributor faulty .
Wiring oily or faulty .
Condenser or coil faulty .
Faulty plugs.
Vacuum advance faulty .
MECHANICAL
Accelerator pump stroke or throttle
linkage improperly adjusted .
Stuck hydraulic lifters.
Intake manifold loose or leaking .
Carburetor mounting loose or leaking.
Valve train damaged or faulty .
FUEL (4)
Fuel pump faulty.
Faulty needle valve and seat .
Float level setting wrong.
Defective parts in carburetor .
Restrictions in fuel lines or filter.
GENERAL
Pre-ignition .
Engine overheating. (Refer to "Engine
Overheats"" in this section) .
Sub-standard fuel .
Overloading vehicle.
Excessive carbon in engine .
Converter defective.
Excessive rolling resistance (Dragging
brakes, tight wheel bearings, underinflated
tires) .
Restricted exhaust.
Dirty air cleaner.
Transmission or power steering faulty .