TM-9-2320-280-34

TRUCK, UTILITY: M998 SERIES

TECHNICAL MANUAL; DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE

JANUARY 1996
TM-9-2320-280-34

  TM-9-2320-280-34 - Page 28 of 1258

TM 9-2320-280-34
Table 2-1.
Mechanical Troubleshooting
MALFUNCTION
TEST OR INSPECTION
ENGINE
1.
ENGINE WILL NOT CRANK
Step 1.
Remove all glow plugs (TM 9-2320-280-20). Using socket and breaker bar at crankshaft pulley,
rotate crankshaft and check for mechanical or hydraulic seizure. If crankshaft will not turn,
replace engine (para. 3-22 or 3-24). If crankshaft turns and liquid is discharged, determine if
liquid is coolant for fuel.
If coolant is discharged, remove cylinder heads (para. 3-4 and 3-5)
and check for cracked cylinder heads or leaking head gaskets. Replace cracked cylinder
heads.
If fuel is discharged, remove and test fuel injection nozzles (para. 4-3). Replace
defective fuel injection nozzles.
Step 2.
Remove converter housing cover (TM 9-2320-280-20) and check for damaged flywheel.
Replace flywheel (TM 9-2815-237-34) if damaged.
END OF TESTING!
2.
ENGINE CRANKS BUT WILL NOT START
Step 1.
Loosen fuel injection lines at injection nozzles and crank engine. If no fuel leaks from fuel
injection lines while cranking engine, replace fuel injection pump (para 4-6).
Step 2.
Remove and test fuel injection nozzles (para. 4-3). Replace defective fuel injection nozzles.
Step 3.
Using compression tester J 6692, elbow NSN 4730-00-985-4804, coupling NSN 4730-01-042-
5266, and adapter J 26999-30, check compression of each cylinder following steps a through f.
(a) Remove all glow plugs (TM 9-2320-280-20).
(b) Remove air cleaner element (TM 9-2320-280-20).
(c) Disconnect lead 54A from fuel injection pump.
(d) Install compression gauge adapter in glow plug hole of cylinder being tested and connect
compression gauge.
CAUTION
Do not add oil to any cylinder when checking compression or damage to engine
may result.
NOTE
Compression reading may exceed 450 psi (3103 kPa).
(e) Crank engine, allow engine to crank long enough to accumulate six compression pulses,
and record highest reading.
(f) Repeat steps (d) and (e) for remaining cylinders.
(g) All cylinders should build up quickly and evenly to a minimum of 380 psi (2620 kPa) and
lowest
reading should not be less than 80% of highest cylinder reading.
Step 4.
Check for warped or damaged cylinder heads. Replace warped or damaged cylinder heads
(para. 3-4 and 3-5).
Step 5.
Check for damaged valves. Replace damaged valves (TM 9-2815-237-34).
Step 6.
Check for damaged or worn pistons and piston rings. Replace pistons or piston rings if worn or
damaged (TM 9-2815-237-34).
END OF TESTING!
3.
ENGINE STOPS DURING NORMAL OPERATION
Step 1.
Perform step 1 of malfunction 1.
Step 2.
Perform steps 1 and 2 of malfunction 2.
END OF TESTING!
2-4


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