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 Section Ill. TROUBLESHOOTING
probable causes of each trouble are listed in the,
15. General
order they are most likely to occur. The pos-
This section provides information useful in
sible remedy recommended is listed opposite
diagnosing and correcting unsatisfactory op-
the related probable cause. Any trouble beyond
eration or failure of the truck and its compo-
the scope of organization maintenance will be
reported to the direct support maintenance per-
nents. Table 1 contains a "Trouble" column, a
"Cause" column, and a "Remedy" column. The
sonnel.
TROUBLESHOOTING CHART
Remedy
Cause
Trouble
Blow horn. If horn does not sound, charge or
Dead battery or loose leads to
Engine will not turn over- - -
replace battery. If horn sounds, check leads
starting motor.
to starting motor terminals.
Piston lock or seizure- - - - - - - - - - - - - - With ignition off, insert a bar in flywheel hous-
ing and try to rotate flywheel. If flywheel
will not turn, report condition to direct
support maintenance.
Charge or replace battery.
Weak battery- - - - - - - - - - - - - - - -
Engine turns but will not
start.
Disconnect 1 spark plug lead and hold it about
Faulty ignition or fuel system- - - - - - - - - -
3/16 inch from the cylinder head while crank-
ing the engine. If a good spark occurs, the
fault is in the fuel system. If there is no
spark, check ignition coil, distributor, and
points (para. 40).
Remove distributor cap. Connect a short piece
Defective distributor- - - - - - - - - -
of high tension cable to high tension terminal
of coil. If no spark occurs when cranking
engine, inspect and replace distributor or
coil, as necesary (para. 40).
Open carburetor feed valve. If this does not
Fuel not reaching carburetor - - - - - - - -
help, check for restrictions in fuel lines and
fuel pump. Remove restrictions.
Turn ignition switch to OFF position and wait
Carburetor flooded- - - - - - - - - -
several minutes before attempting to start
engine.
Fill tank.
No fuel in tank - - - - - - - - - - - - - - -
Clean manifold; replace gasket (para. 23).
Intake manifold leaking or
obstructed.
Adjust gap to 0.030 in. (para. 41).
Spark plug gap improperly set - - - - - -
Clean air cleaner (para. 26).
Air cleaner clogged - - - - - - - - - - -
Engine does not develop
Clean lines.
Fuel lines clogged - - - - - - - - -
full power.
Install new gasket (para. 23).
Manifold leaking - - - - - - - - -
Adjust timing (para. 20).
Improper ignition timing- - - - - - - - -
Correct adjustment (para. 28).
Engine governor improperly
adjusted.
Check clearance (para. 22).
Valve tappet clearance incorrect- - -
Perform compression test (para. 18).
Engine losing compression - - - - - - -
Exhaust clogged - - - - - - - - - - -
Clean exhaust system.
Clean or replace plugs (para. 41).
Spark plug defective - - - - - - - - - - - - - -
Engine misses fire - - - - - -
Replace gasket (para. 21).
Cylinder head gasket leaking - - - - - - -
Tighten manifold nuts or replace gasket (para.
Manifold leaking - - - - - - - - - - - -
Spark plugs improperly gapped- - - - Set gap at 0.30 in. (para. 41).
Contact points sticking or
Clean points and set gap at 0.020 in. (para. 40).
improperly gapped.
Improper ignition timing - - - - - - - Adjust timing (para. 20).
AGO 6217A
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