TM 10-3950-672-24-2
Compression Check
If the air and fuel system are functioning correctly,
perform a compression check to determine whether the
problem is:
Piston ring sealing
Valve sealing
Head gasket sealing or a crack in the cylinder
head
Piston Ring Sealing
If the compression is low but can be increased
significantly by squirting oil into the cylinder, the cause
of low compression is inadequate sealing between the
rings and the cylinder walls.
Normal compression is 2413 kPa (350 PSI] at 250 RPM
cranking speed. A 1007 kPa [100 PSI] difference
between cylinders indicates a compression seal
problem.
Valve Sealing
f the compression is low on one or more non-adjacent
cylinders and the pressure cannot be increased by oiling
the rings, poor valve sealing is to be suspected.
Valve leakage is often audible from the intake and
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