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Re: Compression... (archive)
[ Follow Ups ] [ 2002 Message Board ] [ Msg. Board FAQ ]
Posted by Dwight H. on November 12, 2000 at 23:26:52:

In Reply to: Compression... posted by Jason N. (Atlanta) on November 12, 2000 at 22:41:38:


I just checked the compression on my car... from front to rear, psi's are: 100, 100, 115, 70. What psi should I be getting? it is a '76 2002...8.5:1 comp apparently...

Jason N.
87 325is
76 2002
Atlanta, GA


It should be up around 150 and within 10% of each other. It also needs to be taken with the throttle wide open, did you do this? If you took it with the throttle wide open then this indicates that you have leakage either in valves or rings. Cyl 4 is especially low, probably from a leaky valve. Try injecting a couple of shots of motor oil in each cyl and retake the readings. If they go up significantly, then this indicates worn compression rings. Also put a vacuum guage on an intake vacuum port and start it up. If the needle jumps around then this indicates leakage through an intake valve.
If you retake the compression with the throttle wide open and they are within 10% of each other but are around 100 to 115 then the motor is just showing its age but should run for awhile.

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