Table 4-2. Troubleshooting

TM 10-3930-633-12

is not corrected by the listed corrective actions,

b. This manual cannot list all malfunctions

notify your supervisor.

that may occur, nor all tests or inspections and

corrective actions. If a malfunction is not listed or

Table 4-2. Troubleshooting

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

FUEL SYSTEM

1. FUEL NOT REACHING CARBURETOR.

Step 1. Check fuel level in tank, also check for dirt or sediment in bottom of tank.

Drain and/or refill fuel tank.

Step 2. Check for damaged or leaky fuel lines between fuel tank and carburetor.

Repair or replace damaged fuel lines (para 4-48).

Step 3. Check fuel filter element for obstruction.

Replace fuel filter (para 4-51).

Step 4. Check to see if fuel pump is delivering sufficient fuel.

Replace fuel pump (para 4-52).

2. CARBURETOR NOT DELIVERING PROPER MIXTURE.

Step 1. Check for improper choke adjustment.

Adjust to provide full opening with choke control pushed fully in.

Step 2. Remove carburetor and check for stuck float or blocked fuel passage.

Replace carburetor (para 4-39).

3. HIGH FUEL CONSUMPTION.

Step 1. Check carburetor adjustment.

Adjust carburetor to specifications (para 4-57).

Step 2. Check governor adjustment.

Adjust governor to specifications (para 4-59).

Step 3. Check fuel lines for leakage.

Replace or tighten leaky fuel lines (para 4-48).

Step 4. Check engine operating temperature; overheated engine will use excessive fuel.

Refer to cooling system tests (para 4-64).

Step 5. Check engine timing.

Correct timing to specifications (para 4-38).

Step 6. Check for weak spark.

Refer to ignition system tests (para 4-30).

COOLING SYSTEM

1. LOSS OF COOLANT.

Step 1. Check for leaks at radiator and hose connections.

Replace defective hoses, tighten loose clamps (para 4-64).

Step 2. Check for engine overheating, causing after boil.

Refer to engine overheating tests and inspections.

Step 3. Check for leakage at water pump.

Replace leaking water pump.

Step 4. Check for evidence of water in engine crankcase, indicating cracked cylinder head or blown head gasket.

Replace cylinder head and gasket.

Step 5. Check for evidence of water in transmission fluid, indicating a leak in the oil cooler.

Replace radiator.

2. ENGINE OVERHEATS.

Step 1. Check coolant level.

Fill radiator to proper level.

Step 2. Check for broken or loose fan belt.

Tighten or replace fan belt.

Step 3. Check radiator for obstruction.

Clean away obstruction; steam clean radiator core.

Step 4. Check for proper coolant flow through radiator.

Pressure flush radiator to clear obstructions. Replace thermostat, if sticking.

Step 5. Check ignition timing.

Set timing to specifications (para 4-38).

Step 6. Check water pump for broken impeller.

Replace water pump (para 4-65).

Step 7. Check for restricted air cleaner.

Replace air cleaner element, clear obstruction from air intake system (para 4-54).

Step 8. Check for bent or clogged exhaust pipe or muffler, creating excessive back pressure.

Replace damaged parts (para 4-62).

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