FUEL SYSTEM TROUBLESHOOTING - TM-10-3930-638-24-P0512

TM 10-3930-638-24&P

3-3. ENGINE TROUBLESHOOTING (cont)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

7. ENGINE COMPRESSION TEST (cont)

a . If compression is high, remove cylinder head and check for carbon deposits on cylinder head

and piston crown (para 3-5g). Also, check (use micrometer) if too much material was

removed from resurfaced cylinder head (cylinder head minimum thickness is 3.968 inches)

(notify general support maintenance) (para 4-2b).

b. If compression is low, squirt a teaspoon of engine oil into the affected cylinder and repeat

compression test. If compression gage reading increases to near normal, remove cylinder head

(para 3-5g) and check piston rings and sleeves (notify general support maintenance) (para 4-2f

and 4-2a).

c . If compression gage reading remains low after squirting oil in cylinder, remove cylinder head

(para 3-5g) and check for blown head gasket. If gasket is not damaged, check for burned or

damaged valves and valve seats (notify general support maintenance) (para 4-2b).

d . If compression is low, and items in steps b and c above check satisfactorily, check for head

gasket leakage due to excessive piston sleeve protrusion (notify general support maintenance)

3-4. FUEL SYSTEM TROUBLESHOOTING

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

1. ENGINE IDLE SPEED INCORRECT

Perform fuel injection pump timing and idle speed adjustments (para 3-5a(3)).

a. If idle speed screw on injection pump does not vary engine speed, replace fuel injection pump

b. If idle speed screw on injection pump changes engine speed, but will not adjust to correct

value, check accelerator linkage (para 2-15i). If accelerator linkage checks satisfactory, check

fuel pressure (para 2-10) and fuel injectors (para 3-6b). If above checks are satisfactory,

replace fuel injection pump (para 3-6c).

2. ENGINE NO-LOAD GOVERNED SPEED INCORRECT

Perform fuel injection pump timing and no-load governed speed adjustments (para 3-5a(3)).

a. If high speed screw on injection pump does not vary engine speed, replace fuel injection pump

b. If high speed screw on injection pump varies engine speed, but will not reduce speed to correct

value (no-load speed too high), replace fuel injection pump (para 3-6c).

c. If high speed screw on injection pump varies engine speed, but will not increase speed to

correct value (no-load speed too low), check accelerator linkage (para 2-15i), fuel pressure

(para 2-10) and fuel injectors para 3-6b). If above checks are satisfactory, replace fuel injection

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