I had a garage mechanic do a compression test and he said that all four pistons were all "essentially" at 125 psi.

the communication between us wasn't great but i asked him that I expected it to be around 200 psi. he said 200 psi would only be for diesals.

i have since done some web searching and found out that he might have been doing a "Running compression test" where each cylinder is done 1 at a time with the car idling. I have read that these numbers are typically 1/2 that of the static tests that nearly everyone does here on this forum: this would put the numbers in the ball park of what would be expected.

is anyone familiar with a "Running compression test"?

thanks in advance,

jeff

 

I've heard about it, but I've never done it.

Another possible explanation... He took out one spark plug at a time, putting it back in before doing the next. That way the starter spins more slowly & the results are lower.

You really are only supposed to compare the pressures against each other. Because even a gauge that has a larger internal volume can make the pressures lower.

 

200 psi is the correct compression pressure for a GSR motor.

Go to www.c-speedracing.com in the how to section. It shows the correct procedure for a compression test. If you have a guage, it is really easy to do yourself.

BTW, your mechanic is a dumbass.

 

exactly

 

:werd: and :werd:

 

Yep...dumbass.

Did he do the test while the motor was cold? That will alter the numbers as well.

 

i just moved into town and so i wouldn't want him to be called "my mechanic".

the motor was not cold.

needless to say i won't be going back there and am going to pick up a compression tester.

jeff

 

Engine warmed up, pull all 4 spark plugs.
Pull ECU fuse to disable fuel injection & spark.
Hold the gas pedal floored.
Either crank the same # of revolutions (7?) for all 4, or crank as long as it takes for the pressure to quit increasing.