TM-9-2320-272-24-2
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 2 OF 4
JUNE 1998
TM-9-2320-272-24-2 - Page 687 of 991
TM 9-2320-272-24-2
Table 4-1. Mechanical Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
a.
Remove starter motor (para. 3-82).
b.
If drive gear teeth are broken or missing, replace or repair starter (para. 3-82 or
TM 9-2920-243-34).
c.
Using engine barring tool, turn engine and inspect flywheel ring gear teeth through
starter motor opening in engine block.
d.
If teeth are broken or missing, replace flywheel ring gear (para. 4-15).
END OF TESTING!
4. ENGINE RUNS, BUT MISFIRES
Step 1. Perform malfunction 2.
Step 2. Check for damaged pushrods, camshaft, and tappets.
If damaged, replace (para. 4-20).
END OF TESTING!
5. ENGINE STOPS
Step 1. Check for evidence of engine overheating.
a.
If no overheating is evident, perform malfunction 1.
b.
If overheating is evident, proceed to step 2.
Step 2. Check cooling system.
a.
Check for defective radiator fan clutch drive (TM 9-2320-272-10).
b.
Install fan clutch override bolt (TM 9-2320-272-10) and start engine.
c.
If engine starts and overheats, replace water pump (para. 3-68 or 3-69).
d.
If engine does not start, perform malfunction 2.
END OF TESTING!
6. POOR ACCELERATION AND/OR LACK OF POWER
Step 1. Perform malfunction 2.
WARNING
When performing engine stall check, place wheel chocks in front of
wheels to prevent vehicle from rolling. Failure to do so may cause
injury to personnel and damage to equipment.
NOTE
Perform step 2 for M939A2 engines, model number up to
44629589.
Step 2. Perform engine stall check.
a.
Operate vehicle to stabilize engine and transmission at normal operating temperature.
b.
Check tachometer for proper operation.
4-5
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