TM 10-3950-206-12
Table 4-2. Troubleshooting Chart - Continued
Malfunction
Probable cause
Corrective action
4. Engine misfires.
a. Defective spark plug.
a. If porcelain is cracked, point gap
too wide, or points and porcelain
are coated with soot, replace
or clean plug as required
b. Cylinder head gasket leaking.
b. Replace gasket (para 4-53).
c. Intake manifold leaking.
Tighten manifold nuts or install
new gaskets (para 4-54).
d. Spark plug gap improperly set
d. Set gap at 0.025 inch (para 4-24).
e. Contact points sticking or im-
e. Clean and set point opening at
properly set
0.020 inch (para 4-26g).
f. Improper ignition timing.
f. Correct ignition timing (para 4-50).
g. Low compression.
g. Perform compression test (para
5. Engine overheats
a. Lack of coolant.
a. Fill radiator (para 3-9).
b. Fan and alternator belt loose.
b. Tighten to 3/4 to 1-inch finger
pressure deflection midway
between pulleys (para 4-37c).
c. Cooling system clogged . .
c. Clean and flush system (para 3-9).
d. Thermostat sticking closed.
d. Eliminate sticking or replace
thermostat (para 4-36).
e. Rotted hose.
e. Replace hose (para 4-35).
f. Dirt, insect, or other foreign
f. Blow out with compressed air
matter in radiator.
g. Improper timing.
g. Correct timing (para 4-50).
h. Cylinder head gasket improperly
h. Correct or replace gasket (para
installed.
i. Flow of water is restricted in
i. Inspect cooling system and clean
cylinder head, engine block,
thoroughly (para 3-9).
water jacket, distributing tube
or radiator.
j. Oil cooler or lines restricted or
j. Clean and flush system (para
clogged.
6. Engine runs too hot.
Thermostat sticking closed.
Eliminate sticking or replace thermo-
stat (para 4-36b, c).
7. loss of coolant
a. Radiator leaks.
a. Repair or replace radiator (para
4-35, c).
b.
Cracked cylinder head or block.
b. Replace cylinder head (para 4-53).
c.
Defective water pump.
c. Replace water pump (para 4-38b).
d.
Defective hose connections.
d. Tighten or replace connections.
e.
Faulty cylinder head gasket or
e. Tighten nuts, replace gasket, if
loose nuts.
necessary (para 4-53).
8. Water pump noises.
a. Pulley loose on pump shaft.
a. Tighten pulley (para 4-38b).
b. Impeller broken.
b. Replace water pump (para 4-38b).
c Impeller blades rubbing water
c. Replace water pump (para 4-38b).
pump housing
9. Rapid fan and alternator
a. Belt adjusted too tight or too
a. Adjust to 3/4- to 1-inch finger
belt breakage or wear.
loose.
pressure deflection midway
between pulleys (para 4-37).
b.
Incorrect type belt.
. Use correct belt.
c.
Oil on belt.
c. Clean belt.
d.
Misalignment of pulleys.
d. Align properly.
e.
Broken or rough flanges on fan
e. Repair pulleys as necessary or re
pulley, alternator pulley.
place alternator pulley (para
10. Fan noises.
a. Belt adjusted too tight (squeak).
a. Adjust to 3/4- to 1-inch finger
pressure deflection midway
between pulleys (para 4-37c).
b. Belt adjusted too loose (squeak
b. Adjust to 3/4- to 1-inch finger
on acceleration).
pressure deflection midway
between pulleys (para 4-37c).
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