Section V. TROUBLESHOOTING - TM-5-4320-243-150043

Section IV. OPERATOR'S MAINTENANCE

3-8. General

water at proper intervals.

Refer to the MAC

Maintenance to be performed by the operator is limited

(maintenance allocation chart) Appendix C.

to the replenishment of fuel, oil, coolant, and battery

Section V. TROUBLESHOOTING

3-12. Engine Knocks or Develops Unusual Noise

3-9. General

Probable cause

---- Possible remedy

This section provides information useful in diagnosing

Crankcase oil supply too ---- Aid oil to proper level.

and correcting unsatisfactory operation or failure of the

low.

---- Refer to figure 3-1.

pumping assembly and its components. Each trouble

Caution

symptom state is followed by a list of probable causes.

If the engine knocks or is noisy

The possible remedy recommended is described

when the crankcase is filled with oil

opposite the probable cause. Any trouble beyond the

to its proper level, stop the engine

scope of organizational maintenance shall be reported

immediately

and

report

the

to direct support maintenance.

condition to field maintenance.

In troubleshooting, never make more than one

Continued operation of the unit

adjustment at a time; then locate the trouble by a

under these conditions can cause

process of elimination. Usually the cause will be Simple

serious damage to the engine.

rather than complex.

Accessory mountings ---- Tighten all loose connec-

loose.

---- tions.

If the engine cranks over but fails to start, for example,

Valve adjustment incor- ---- Adjust valves (p ara 3-36).

the trouble is almost certainly either in the ignition or the

rect.

fuel system, and a quick check should determine which

Timing incorrect

---- Adjust engine timing (para

system to examine further.

3-49).

3-10. Engine Fails to Start or Is Hard to Start

3-13. Engine Stops Suddenly

Probable cause

Possible remedy

Probable cause

Possible remedy

Fuel tank empty

---- Fill fuel tank.

Fuel tank empty

---- Fill fuel tank.

Air cleaner clogged

---- Service air cleaner (para

Air cleaner clogged

---- Service air cleaner (para

3-4).

Spark plugs defective ---- Adjust or replace spark

Oil pressure too low

---- Add oil to the proper level.

plugs (para 3-50).

Refer to figure 3-1.

Carburetor defective

---- Replace carburetor (para

Fuel pump defective

---- Replace fuel pump (para

3-40).

3-39).

Magneto defective

---- Replace magneto (para

Coolant too hot

---- Fill cooling system (para

3-49).

3-55). Replace defective

Magneto contacts not ---- Adjust magneto contacts

thermostat (para 3-59).

closing.

para 3-49).

Replace defective V-belts

Fuel pump defective

---- Replace fuel pump (para

para 3-58).

3-39).

Caution

Cranking motor fails to ---- Refer to paragraph 3-48.

Never

add

coolant

crank engine.

excessively hot engine block.

3-11. Engine Misses or Runs Erratically

Failure to observe this caution may

Probable cause

Possible remedy

result in damage to the engine

Air cleaner clogged

---- Service air cleaner (para

block.

3-4).

Spark plugs defective ---- Adjust or replace spark

3-14. Engine Overheats

plugs (para 3-50).

Probable cause

Possible remedy

Spark plug leads defec- ---- Replace leads (para 3-50).

Crankcase oil too low ---- Add oil to proper level. Re-

tive.

fer to current lubrication

Probable cause

Possible remedy

order.

Governor defective

---- Replace governor (para

Coolant low in radiator ---- Fill cooling system.

3-41).

Valve adjustment incor- ------ Adjust valves (para 3-36).

rect.

3-14