LOW COMPRESSION ? Or Stater Problem?
 

Hello RX7 CLUB, today I do compression test an RX7 S5 that have been rebuild only 1 years and it have 5000 mileage on it. It have goopy apex seal. I have a joy ride with it around the block it pull great and really loud. However, when i test the compression test it only read 55 psi on both front and rear. Not sure it's because of the stater and battery or it have bad compression. Let me know what u guys think thanks. BTW I test it with craftsman compressor tester so it a little bit longer than the regular one so not sure that will cause the low compression.

If you have a tachometer you can correct for cranking rpm while doing your compression test. There is a chart in the Factory Service Manual.

However, unless you have been running the car without proper oiling I would be suspicious of that measurement. A rebuilt engine with that little mileage should have very good compression unless it has been abused. Does your car consume oil?

I would do the test again but maybe go buy a different compression tester. Your results sound odd.

Well it run with premixed fuel.The owner said he didn't drive it much after the rebuild since he too busy with work.I think I may get different compression tester to see if anything change.

Any solution for this ? Thanks

Did you get another compression test done?

Also, why are you so concerned about it? Are there any symptoms you are experiencing that indicate low compression (lumpy idle, poor starting)?

If you aren't having any symptoms, I just wouldn't worry about it. At least until you can get another tester.

EDIT: I'm sorry, I thought the car was yours. It seems based on your first post that you are looking at buying it and you want a test first. I take back what I said above, it is a good idea to get proper compression numbers to make sure the engine is healthy. But you still need to try another tester as I suspect the first one is not working properly.

No it fine, am glad you help. and yeah I came back after two days with 2 different compression tester and bring a battery as well since his battery is dead. After Install my battery in, the car started after 2 second. Then we let the car idle to warm up around 5-8 mins then we shut it down and start do compression test. 1st I try to do the BUMP test, as I crank the engine, the dial bounce 60,0,60,0,65 which is around 10 to 15 psi higher than the last time we did. Then I also try compression test, then dial show max is at 65 psi. The owner said maybe it was a bad starter and bad starter fuse. So I am not sure what to do now. Been wasting $60+ on gas from driving to check this car. (Thanks for your help by the way)
And btw it have Mild street port with 6 ports. I really like the car but I just want to know if there anyway to check if it's a bad apex seals or something that cause the engine to have low compression.

well, first of all, i wouldn't run those seals in an n/a so that right there is an immediate mistake.

If your test is showing 60,0,60, it already needs the engine tore apart

i think he is counting the end of pulse as 0

Ahh yes, now that i look at it again i agree

Still low numbers either way

Unless it isn't fully broke in, but even still i don't see them coming up much