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 940 of 991
TM 9-2320-272-24-2
4-34. INJECTOR PLUNGER AND VALVE ADJUSTMENTS (TORQUE METHOD) (Contd)
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
CAUTION
Before checking or setting valve clearances, ensure crossheads are
adjusted.
NOTE
l
Crossheads operate two valves with one rocker lever. Crosshead
adjustments are necessary to ensure equal operation of each
valve.
l
The same engine position used in adjusting injectors is used for
setting intake and exhaust valves.
Loosen locknut (7) attached to adjusting screw (1) on crosshead (6).
Back out adjusting screw (1) on crosshead (6) one turn.
Apply light finger pressure to rocker lever contact surface (2) to maintain crosshead (6) contact with
valve stem (4) opposite adjusting screw (1).
Turn adjusting screw (1) down until it touches valve stem (5).
Tighten locknut (7) 22-26 lb-ft (30-35 N•m).
Hold adjusting screw (1) with screwdriver and tighten locknuts (7) 25-30 lb-ft (34-41 N•m).
Check crosshead (6) valve spring retainer (3) clearance with wire gauge. At this point, there must be
a minimum clearance of 0.020 in. (0.51 mm).
Loosen locknut (8) on intake rocker lever (11) and back out adjusting screw (9).
Insert feeler gauge between rocker lever (11) nose and crosshead (6) on cylinder (10). Refer to table
4-6 for valve clearance settings.
Using screwdriver, slowly turn down adjusting screw (9) until intake rocker lever (11) nose touches
feeler gauge.
Check intake rocker lever (11) clearance by removing and inserting feeler gauge. There will be a
slight drag on feeler gauge when clearance is correct.
Hold adjusting screw (9) firmly in position on cylinder (10) to prevent adjusting screw (9) motion,
and tighten locknut (8) 40-45 lb-ft (54-61 N•m).
Repeat steps 15 through 19 to adjust exhaust rocker lever (12).
Rotate pulley (13) so pointer (15) is at next timing mark (14) and perform injector and valve
adjustments for cylinder indicated by VS mark (rocker levers are loose).
Rotate pulley (13) after each set of injector and valve adjustments until all timing is completed.
Table 4-6. Valve Clearance Inch (MM) (Torque Method).
Intake valves
Exhaust Valves
Cold Set
Cold Set
Aluminum Rocker Housing
0.014 in. (0.36 mm)
0.027 in. (0.79 mm)
4-258
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