GMC 1976 ZEO 6083 Maintenance Manual page 272

ENGINE TURNS OVER AT NORMAL SPEED BUT DOES NOT START
OR STARTS HARD (7)
NOTE :
If ignition is set too far advanced, spark may occur too early when engine
is cranked. The first (and only) explosion runs the engine backward . A kickback
may jam the starter or break the starter drive housing.
IGNITION (2)
OPEN PRIMARY
Burned or oxidized ignition points .
Coil resistance unit burned out or open .
Starting switch ignition coil resistance
by-pass circuit open .
Ignition points not closing.
Breaker arm binding on pivot post, pre-
venting closing of points .
Breaker arm spring weak or broken .
Breaker arm distorted or bent .
Dirty ignition points .
Primary lead connection loose at distrib-
utor or coil .
Primary windings in coil broken .
Open ignition switch circuit.
GROUNDED PRIMARY
NOTE :
A grounded coil primary winding, a
grounded ignition switch, or a grounded switch-
to-coil primary lead will cause excessive current
flow and will usually cause wires to burn .
Ignition points not opening or closing due
to wear or improper adjustment .
Faulty bushing in breaker arm.
Cracked or faulty insulator at distributor
primary terminal .
Grounded or faulty condenser.
Distributor-to-coil lead grounded .
Primary coil winding grounded .
Broken or loose ignition wire or faulty
switch .
MECHANICAL
Choke binding, sticking, or improper
adjustment .
Low or erratic compression. (Check valve
train mechanism, rings, blown head gasket,
etc.)
FAULTY SECONDARY (6)
Corroded spark plug cable terminals.
Chafed or cracked cable insulation .
Ignition coil weak or inoperative.
Moisture on ignition coil, terminals, dis
tributor cover, spark plug procelains, or in
distributor .
Improper type of spark plugs.
Cracked distributor cap or a burned carbon
track from distributor cap center terminal to
housing.
Improper installation of spark plug cables
(not correct for firing order) .
Spark plugs damaged, dirty, or wet, porce-
lains cracked, or gaps improperly spaced .
Rotor contact spring bent or broken .
Distributor rotor grounded.
Distributor cap center terminal (inner)
broken or missing.
Broken or burned out radio suppressor in
distributor cap.
FUEL (11)
Hot engine vapor lock .
No fuel or insufficient fuel .
Water and/or dirt (Fuel System).
Excessive fuel. (4)
Accelerator pump faulty . (8)
Fuel pump worn or defective.
Fuel filter dirty.
Carburetor dirty or defective.
Vent in fuel tank clogged or restricted .
Carburetor mounting bolts loose.
GENERAL
ENGINE 6A- 7
Check proper starting procedure (setting
choke, accelerator pumping, accelerator
position etc.) .
Air cleaner dirty.
Engine timing .
Restricted exhaust.
Poor ground or faulty wiring .