Compression Testing
Testing the engine for compression is not a normal part of
a scheduled maintenance procedure, but is important
when trying to diagnose engine power or unusual perfor-
mance related problems with the engine.
Before performing a compression test, be sure the bat-
tery is fully charged and valve clearances are correctly
adjusted. See page 7-12. Be sure the air cleaner and
exhaust systems are free of obstructions, to prevent a
false or low reading
The engine should warmed up for approximately 5 min-
utes prior to compression testing.
To Perform Compression Test:
1 Move the loader to a level surface, lower the boom
arms, engage the parking brake and shut off the engine.
Remove the ignition key for safety.
2 Access the engine by opening the rear door and rais-
ing the engine compartment cover.
3 Disconnect the wiring plug connection on the engine
stop solenoid. This will prevent fuel flowing to the engine
when the engine is turning over.
4 Clean dirt from the top of the engine area to prevent
contaminants entering the engine.
5 Remove the fuel injection pipes from the fuel injec-
tors. (fig. C3631) If the injector pipes are corroded or the
pipes twist with the nut when loosening, replace the injec-
tion pipe before putting the loader back into service. Cap
the open lines and injectors to prevent contamination
entering the fuel injection system.
6 Remove the fuel transfer lines from the injectors.
7 Remove the fuel injectors from each cylinder. Use
caution. Do not damage the injector while removing from
the cylinder head.
8 Connect a compression tester (see Special Tools in
Section 8) to the cylinder to be tested. (fig. C179) Be sure
to use the correct thread on the adapter screwed into the
injector hole.
9 Rotate the engine with the starter (200 ~ 300 RPM)
2 ~ 3 complete revolutions. Note the compression reading
on the gauge. Repeat the process again to verify the first
test reading.
10 Continue the compression test and the remaining
cylinders keeping written notes of all the registered test
readings.
11 Compare the compression test readings with the
specifications given in Section 7.4, pg. 7-24, Engine
Specifications.
continued...
7-13
C3631
C179
Injector hole
Compression tester
Injector pipe
Injector
Transfer line
CYLINDER HEAD 7.2
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