TM-5-3805-254-14-P-2

TRUCK, DUMP, 20 TON, 6X4, ON-OFF HIGHWAY 71,000 GVW, IHC MODEL F-5070 (CCE)

TECHNICAL MANUAL; OPERATOR’S, ORGANIZATIONAL, DIRECT SUPPORT, GENERAL SUPPORT AND DEPT MAINTENANCE MANUAL (INCLUDING REPAIR PARTS INFORMATION AND SUPPLEMENTAL MAINTENANCE INSTRUCTIONS)

JUNE 1980

TM-5-3805-254-14-P-2 - Page 364 of 894

TRUCK SERVICE MANUAL

CAUTION

Never vacuum test cylinder head with injectors installed.

Installation of injectors while head is removed from block

could cause misalignment of valves in valve seat area

and result in leakage during testing which would not

necessarily occur during actual engine operation.

1. Operate vacuum pump until hand on vacuum

gauge (1,

Fig.

2-13) reaches 18 to 25 inches vacuum.

Close shut-off valve (2), release push-button to stop

pump.

2. Time fall of gauge hand as follows:

a.

Begin

timing as soon as hand reaches "18" on dial.

b. Stop timing when hand reaches "8." c.

If

elapsed time is less than ten seconds, valve seat is

unsatisfactory.

3. Tap stem end of valve with a soft-faced mallet

and retest.

If valve seat is unsatisfactory:

a. Check for leaking connections in tester; operate

vacuum pump against a clean window glass or any

smooth flat surface; fall of indicator hand indicates a

loose connection.

b. Check valve and seat face area to be sure they

are free of dirt particles.

4. Regrind seat and reface valve if necessary;

however, it is possible to mistake leakage around valve

seat insert for valve seat leakage.

If this type leakage is

suspected, apply