TM 9-2320-272-24-2
Table 4-1. Mechanical Troubleshooting.
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
ENGINE
1. ENGINE WILL NOT CRANK
Step 1. Check for mechanical or hydraulic seizure. Remove fuel injectors before attempting
crankshaft rotation test (para. 4-12 or 4-55).
a. Try to rotate engine manually using engine barring tool.
b. If crankshaft will not rotate, go to step 2.
c. If crankshaft rotates, check if liquid is discharged.
e. If liquid is fuel, replace fuel injectors (para. 4-32 or 4-55).
Step 2. Engine must be removed and inspected for extent of internal damage (para. 4-6).
END OF TESTING!
2. ENGINE CRANKS, BUT FAILS TO START
Step 1. Check for defective fuel shutoff valves (M939/A1).
Remove, inspect, and replace fuel shutoff valve if necessary (para. 4-36 or 4-37).
Step 2. Check for broken fuel supply pump driveshaft.
a. Remove tachometer cable from fuel pump, crank engine, and observe if tachometer
driveshaft end of pump is rotating.
b. If driveshaft does not rotate, replace fuel pump (para. 4-35 or 4-57).
Step 3. Check fuel injector and valve adjustment (para. 4-33 or 4-56).
Step 4. Check for dirty, plugged, and damaged fuel injectors.
If dirty, plugged, or damaged, clean or replace fuel injectors as necessary (para. 4-32 or 4-55).
WARNING
Diesel fuel is flammable. Do not perform fuel system procedures
near open flame. Injury to personnel may result.
NOTE
Perform step 5 for M939A2 series vehicles.
Step 5. Check fuel injection pump for proper operation.
a. Loosen two injector tubes on fuel pump injectors.
b. Crank engine and visually inspect fuel delivery.
c. If no fuel is present, replace or repair fuel injection pump (para. 4-57).
END OF TESTING!
3. ENGINE STARTER MOTOR OPERATES, BUT DOES NOT ENGAGE FLYWHEEL RING GEAR
Check starter drive gear and flywheel ring gear for broken and missing teeth.
4-4
