GMC 1976 ZEO 6083 Maintenance Manual page 271

6A- 6 ENGINE
ENGINE TURNS OVER AT NORMAL SPEED (1)-STARTS HARD
WHEN HOT (7) (11)
NOTE : This condition is usually caused by an over-supply of fuel due to any of
the items listed under "Does Not Start" due to excessive fuel supply .
GENERAL
Check proper starting procedure (setting
choke, accelerator pumping, accelerator
position, etc.) .
Engine timing and dwell.
Air cleaner dirty .
Engine overheating. Refer to ENGINE OVERHEATS
in this section.
MECHANICAL
Choke mechanism binding, sticking and/or
improper adjustment. (3)
ENGINE STARTS - FAILS TO KEEP RUNNING OR STALLS HOT OR
COLD (7)
GENERAL
Vapor lock . (11)
*Engine overheats.
*Engine runs too cool .
Idle speed too low.
Positive crankcase ventilation valve.
Leak in intake manifold (vacuum line faulty
or disconnected) . (9)
Exhaust crossover in intake manifold
plugged.
Exhaust system restricted .
Air-intake restricted .
Carburetor icing. (5)
Engine timing and dwell .
MECHANICAL
Throttle linkage defective or improperly
adjusted .
Valve train faulty .
Valve lifter or valve clearance.
Low compression .
Choke valve faulty, stuck, or binding. (3)
Head cracked or gasket leaking.
Excessive engine friction .
FUEL
Vapor lock .
Flooding. (4)
Accelerator pump . (8)
Carburetor faulty .
Fuel pump faulty .
Fuel restricted .
IGNITION
Check for faulty spark plugs. (6)
FUEL
Dirt and/or water in fuel system .
Faulty fuel pump .
Float level too high. (4)
Idle adjustment incorrect.
Idle compensator valve faulty .
Needle valve seat faulty .
Mixture too rich or too lean .
Faulty carburetor .
IGNITION
Spark plugs damp or dirty and/or gap
incorrectly set or not installed properly .
Faulty coil or condenser.
Distributor points incorrectly set, burned,
pitted or dirty .
Distributor advance mechanism faulty or
timing improperly set.
Worn rotor or distributor cap loose, cor-
roded, poor connections, or incorrect wiring .
*Refer to ENGINE OVERHEATS in this section .