Checking Cylinder Compression

4-22. Checking Cylinder Compression

a. General. For instructional purposes in

this section all fuel injector nozzle and holder

assemblies will be removed and a compression

test will

made

on a l l c y l i n d e r s . I f

troubleshooting indicates that only one cylinder

requires a compression check, it may be done by

rem oving the nozzle from the questionable

cylinder.

Warning; When only one cylinder is checked,

there is the possibility of the engine firing on the

other cylinders when compression check is being

m a d e . To prevent engine firing, remove all

Install

nozzles then check cylinder compression. Unless

1. Position new fuel injectc r nozzle gasket (A) on end of

compression adapter - 4!'10-795-7961. Apply a light

all nozzles are removed, the engine motoring rpm

coating of grease on gasket so it adheres to adapter

will be below desired cylinder checking rpm.

when installed in cylinder.

b. Starting Engine. C h e c k t h e v e h i c l e

Note. Be sure gasket is installed with open

batteries to assure full charge and replace if

face toward adapter.

necessary. R e f e r to the pertinent operator's

2. Install adapter (B) into fuel injector nozzle holder

manual for engine starting procedures. Start

opening and tighten securely using fixed open end

engine a n d allow engine t o r e a c h n o r m a l

wrench - 5120-871-7198

Remove

operating temperature and then stop engine. Cut

1. Remove adapter (B) frc m fuel injector nozzle holder

off fuel supply so engine will not deliver fuel

opening using fixed open end wrench -5120-871-7198

while performing compression test.

as shown in figure 4-16$.

c. Compression Test. R e m o v e t h e f u e l

2. Remove and discard gasket (A).

injector nozzle and holder assemblies from each

Figure 4-184. Installing or removing compres-

cylinder (para 4-17). Install the compression

sion adapter--4910-795-7961 (cylinder

checking adapter and compression gage (figs. 4-

compress:ion test).

1 8 4 and 4-185) and motor engine with the

starter motor. Crank engine several seconds, or

u n t i l compression gage reaches

maximum

reading. Cylinder compression pressure should

b e between 330 and 480 psi. High cylinder

pressures are caused by combustion of lubrica-

ting oil in the engine combustion chamber. If this

occurs, allow combustion gases to escape prior to

taking compression reading.

4-94