Chevrolet Light Duty Truck 1973, Service Manual

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6-68 ENGINE
a.
c.
d.
e.
DIAGNOSIS
ENGINE FAILS TO START
CAUSE
Corroded or loose battery terminal connections f.
and/or weak battery.
Broken or loose ignition wires and/or faulty
ignition switch.
Excessive moisture
system.
on plugs, caps or ignition
Damaged distributor rotor, cracked distributor cap
and/or corroded distributor contact points.
Fouled spark plugs and/or improper spark plug
gaP-
h.
i.
j-
k.
Weak or faulty coil.
Carburetor flooded and/or fuel level in carburetor
bowl not correct.
Dirt and water in gas line or carburetor.
Sticking choke.
Faulty fuel pump.
Faulty solenoid or starting motor.
Park or neutral switch inoperative.
ENGINE LOPES WHILE IDLING
CAUSE
a.
b.
c.
d.
Air leaks between intake manifold and head.
Blown head gasket.
Worn timing chain or sprockets.
Worn camshaft lobes.
e. Overheated engine.
f. Plugged crankcase vent valve.
g. Faulty fuel pump.
h. Leaky exhaust gas recirculation valve.
ENGINE MISSES WHILE IDLING
CAUSE
a. Spark plugs damp or gap incorrectly set.
b. Excessive moisture on ignition wires and caps.
c. Leaks in ignition wiring.
d. Ignition wires making poor contact.
e. Uneven compression.
f. Burned, pitted or incorrectly set contact points.
g. Faulty coil or condenser.
h. Worn distributor cam or cracked distributor cap.
i. Incorrect carburetor idle adjustment and/or dirty
jets or plugged passages in carburetor.
ENGINE MISSES AT VARIOUS SPEEDS
CAUSE
j. Foreign matter, such as dirt or water, in gas line or
carburetor.
k. Air leak at carburetor mounting gasket.
1. Choke inoperative.
m. Faulty spark advance mechanism.
Burned, warped, pitted, or sticking valves.
Incorrect valve lifter clearance.
Low compression.
Leak in exhaust gas recirculation valve.
a. Dirt and water in gas line or carburetor.
j-
Insufficient point dwell.
b. Fouled carburetor jets.
k. Detonation or pre-ignition.
c. Incorrect ignition timing.
1. Excessively worn fuel pump diaphragm.
d. Points dirty, pitted or incorrectly spaced.
m. Weak valve spring.
e. Excessive play in distributor shaft.
n. Worn camshaft lobes.
f. Insufficient spring tension on points.
o. Engine overheating.
g-
Distributor cam lobe worn.
P- Sub-standard fuel.
h. Weak coil or condenser.
q-
Leak in exhaust gas recirculation valve.
i. Spark plugs dirty or damp and/or gaps set too wide.