Compression Test.

[Wells]

So a friend was doing a compression test ..

and comparing the numbers with this website ..


http://www.dsmgrrrl.com/FAQs/compression.htm


178 is supposed to be the standard compression, and 133 is supposed to be the "service limit" ..


He had 130 130 150 150 ... So what does that mean? There isn't anyway to fix that other than rebuilding the motor, right?

 

[2gGSX]

Add a capfull of oil to each cylinder well and then run the test again. Were you at WOT with a full charge on the battery when you performed the test? If you have any doubts that your compression tester is off then test it again with another one to see if you get the same results. Otherwise, it looks like you just have a very tired motor that will be due for a rebuild soon due to the discrepancy between the 1/2 and 3/4 cylinder numbers as well as low overall numbers. Sorry bud

 

[playitlouddsm]

Time for the bottom end rebuild. Looks like the rings are shot.

 

[Wells]

It has 125,000 miles if I remember right.

 

[2gAWDTalon]

In the service manual there is those specs you gave and also a spec for the difference between cylinders. I do not remeber what it is, but it is WAY less then 20.

 

[diablos991]

Be sure that you performed the test on the engine while it was at operating tempurature, and while holding the throttle completely open.

Failing to do either of these would lower compression.

 

[copper_gst]

I too just did a conprestion test and my numbers where 133, 135, 125, 145. Acorrding to the shop that performed the test, the problem is most likely the piston rings. I would make sure that you DO have the engine at normal running temp because metal expance when hot so it seals better. If you are not sure take it to a shop and have them do it. It usally only cost around $30 and then you can ask them for their thoughts on it. Hope that helps.

 

[daren_p]

The variance between cylinders is 14 psi max. Like was said make sure the car was run to operating temperatures, battery fully charged, throttle plate open and cranked atleast 4 times or until stable reading. If you still get the same results add some oil (1-2 table spoons) to each cylinder to see if the compression jumps at all. If compression jumps more then 30 psi, rings are probably worn. If not then its time to do a leak down test.