Compression Test Results

[Blu92]

Tried searching but couldn't quite find what I was looking for. Just did a compression check on my car(1992 GSX). Warmed the car up first and the first readings were #1, 175 #2, 175 #3, 177 #4, 175. I did it two more times for an average. The second time I got 140,140,140,145. Then I realized I didn't push in the gas pedal so I did for the third test and got the exact same results as the second one. Was wondering what could cause that difference between test and at about 140 should I think about rebuilding some time soon. It's pretty much a stock car, only a 3 inch exhaust and bse( stubby shaft and left front shaft in) when I did my timing belt recently. Going to do a leak down test tomorrow.

 

[oneslowwdsm]

Sounds like you may have weakened the battery on the first compression tests yielding lower results when you did it again.

 

[Blu92]

I was wondering that. Car sat for a month while I was doing the timing, replacing motor mounts, and rebuilding steering rack. Had to jump it to start it and wouldn't hold a charge. Put distilled water in the cells cause they were low and took it to advance to get a slow charge. Holds a charge now but could be weak after that cranking. I'll do the leak down tomorrow since that won't wear the battery out.

 

[GST with PSI]

I typically hook the car up to a battery charger when I do my compression tests. That alleviates any variation due to voltage drop over long periods of cranking.

Overall, your results look pretty good. Variation between cylinders is what you should really be worried about. Your results don't really show much variation, which is good.

 

[92AWDHX40]

car runs ok though no over heating or issues.

 

[Blu92]

Doesn't overheat. Just replaced the thermostat and flushed the coolant. When it's warming up it will surge 2 or 3 times but sits at 800 rpms when it warms up.