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 Section IV. TROUBLESHOOTING
probable causes of the trouble. The corrective action
This section contains information useful in diagnosing
recommended is described opposite the probable
and correcting unsatisfactory operation or failure of
cause.
the truck. Malfunctions which may occur are listed in
Table 2-2. Troubleshooting
Probable cause
Malfunction
Corrective action
a. Ignition switch defective.
a. Replace switch.
1. Engine will not start (no spark. Am-
b. Repair or replace and tighten.
b. Ignition primary wires or starting motor
meter shows no discharge. Zero read-
cables broken or connections loose.
ing with ignition switch on).
c. Replace coil (para 2-36).
c. Ignition coil primary winding open.
d. Clean and adjust points (para 2-34).
d. Distributor points dirty.
e. Adjust or replace points (para 2-34).
e. Distributor points not closing.
f. Remove, clean, reinstall, tighten cable
f. Loose or corroded ground or battery cable
lamps (para 2-37).
connection.
a. Replace defective parts (para 2-34).
a. Short-circuited or burned distributor cap or
2. Engine will not start (ammeter shows
abnormal discharge with ignition
rotor.
b. Short-circuited wire between ammeter and
b. Repair or replace wire.
switch on).
Ignition switch.
c. Replace coil (para 2-36).
c. Short-circuited primary winding in ignition
coil.
a. Distributor points not opening.
a. Clean or replace and adjust points (para
3. Engine will not start (weak spark or
no spark).
b. Distributor points pitted or burred.
b. Clean or replace (para 2-34).
c. Distributor capacitor weak.
c. Replace capacitor (para 2-34).
d. Ignition coil weak.
d. Replace coil (para 2-36).
e. Primary wire connections loose.
e. Tighten connections.
f. High-tension wires, spark plug wires, or dis-
f. Dry thoroughly.
tributor cap wet.
g. High-tension wires, spark plug wires, or dis-
g. Replace defective parts.
tributor cap damaged
h. Distributor cap or rotor burred or broken.
h. Replace defective parts (para 2-34).
i. Spark plug gaps incorrect.
i. Reset gaps (para 2-35).
j. Short-circuited secondary circuit in ignition
j. Replace coil (pars 2-36).
coil.
4. Engine will not start (good spark).
a. Fuel tank empty.
a. Refill tank.
b. Dirt or water in carburetor or float switch.
b. Replace carburetor (para 2-17).
c. Carburetor and engine flooded by excessive
c. Depress accelerator pedal fully and crank
use of choke.
engine:
d. Inspect for damaged or leaky lines or air
d. Fuel not reaching carburetor.
leak into line between tank and fuel pump.
e. Disconnect lines, drain tank and blow out
e. Dirt in fuel lines or tanks.
lines (para 2-21).
f. Repair or replace line.
f. Fuel line pinched.
g. Install wires correctly.
g. Ignition wires incorrectly installed
in dis-
tributor cap.
h. Reset timing (para 2-14).
h. Ignition timing incorrect.
i. Replace fuel pump (para 2-18).
i. Fuel pump not pumping.
j. Report to direct support maintenance.
j. Lack of engine compression.
a. Reset timing (para 2-14).
a. Ignition out of time.
5. Engine backfires.
b. Install wires correctly.
b. Spark plug wires incorrectly installed
in dis-
tributor cap or at spark plugs.
c.
Replace cap (para 2-34).
c. Distributor cap cracked or shorted.
d.
Report to direct support maintenance.
d. Valve holding open.
a.
Reset timing.
a. Improper ignition timing.
6. Engine operates erratically.
b.
Install wires correctly.
b. Spark plug wires incorrectly installed
in dis-
tributor cap.
c. Drain carburetor, clean fuel system.
c. Dirt or water in carburetor.
d. Adjust carburetor (para 2-17).
d. Carburetor improperly adjusted.
e. Report to direct support maintenance.
e. Valve sticking, not seating properly,
burned
or pitted.
2-3
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