TM-9-2320-272-24-4

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 4 OF 4

JUNE 1998

TM-9-2320-272-24-4 - Page 284 of 836

TM 9-2320-272-24-4

5-37. FUEL INJECTION PUMP CALIBRATION (Contd)

l. Low Idle Fuel Delivery Test

1.

Set fuel pump (1) to 300 rpm.

2.

Position control lever (6) against idle stopscrew (5) and take a fuel draw.

3.

Observe control rack travel. Correct control rack travel should be 0.308-0.316 in. (7.80-8.03 mm).

4.

With test stand set at 1,000 strokes, take fuel draw and check delivery quantity. Correct delivery

quantity is 0.824-1.373 in.

3

(13.5-22.5 cm

3

).

5.

If fuel delivery deviates from specifications, adjust idle stopscrew (5) until correct fuel delivery is

obtained.

m. External Stop Setting

Perform this task so control rack has a 0.039 in. (1 mm) preload.

Failure to do so may result in damage to fuel pump.

1.

Loosen adjusting nut (3) on throttle stopscrew (4).

2.

Position throttle lever (2) against throttle stopscrew (4).

3.

Adjust throttle stopscrew (4) until 0.039 in. (1 mm) preload is observed on dial indicator (7) and

tighten adjusting nut (3).

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