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 684 of 991
TM 9-2320-272-24-2
MECHANICAL TROUBLESHOOTING INDEX
MALFUNCTION
NO.
MALFUNCTION
TROUBLESHOOTING
PROCEDURE
PAGE
40.
41.
42.
43.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
25.
26.
27.
22.
23.
24.
20.
21.
14.
15.
16.
17.
18.
19.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
ENGINE
Engine will not crank
........................................
Engine cranks, but fails to start.
...............................
4-4
4-4
Engine starter motor operates, but does not engage flywheel ring gear.
..
4-4
Engine runs, but misfires
.....................................
Enginestops.
. .............................................
4-5
4-5
Poor acceleration and/or lack of power
...........................
4-5
Low oil pressure
............................................
4-6
Contaminated engine oil
.....................................
Excessive oil consumption.
....................................
4-7
4-7
Air cleaner element clogged with oil
............................
4-7
Engine knocks (mechanical noise)
..............................
4-7
Excessive engine vibration
....................................
Excessive gear noise
.........................................
4-7
4-7
FUEL SYSTEM
Engine idle rough, erratic.
....................................
4-7
Excessive fuel consumption.
...................................
4-8
Engine surges at idle speed.
...................................
Engine surges at all speeds.
4-8
4-8
...................................
Excessive exhaust smoke at idle, and under load.
..................
4-8
Engine fails to stop
..........................................
Engine misses
4-8
..............................................
4-8
Low power or loss of power.
...................................
Engine overspeed
...........................................
4-9
4-9
Engine lubricating oil diluted by fuel
............................
Engine fuel knocks
..........................................
4-9
4-9
COOLING SYSTEM
Engine overheats.
...........................................
4-9
Loss of coolant.
.............................................
4-9
Contaminated coolant.
.......................................
4-9
TRANSMISSION
Transmission shifts occur at too high a speed.
.....................
4-9
Transmission shifts occur at too low a speed
......................
4-9
Low main operating pressure at all shift ranges
...................
4-10
Clutch slippage in all forward and/or reverse gears
.................
4-10
Excessive vehicle creep (first and reverse)
........................
4-10
Vehicle moves in neutral.
.....................................
4-10
No response to shift lever movement
............................
4-10
Oil thrown out of oil tiller tube.
................................
4-10
Oil leaking into converter housing
..............................
Rough shifting.
.............................................
4-10
4-11
Transmission oil dirty, foamy, and/or milky
.......................
Oil leak at output shaft.
......................................
4-11
4-11
TRANSFER CASE
Transfer case will not shift into gear
............................
4-11
Transfer case will not stay in gear
..............................
4-12
Excessive noise during operation
...............................
4-12
Lubrication leaks
...........................................
4-12
4-2
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