Compression Test

[UTGAMER]

So I finally get around to doing the test and it starts raining.


I was needing to ask yall what should the psi gauge read? I only got to check 1 cylinder and its was maybe 65, but the ignition coil was still hooked up and engine was cold. I cant get car to run to warm it up

 

[UTGAMER]

Also it says if it compression goes up after adding oil it is worn pistons, but if it stays the same that its leakage in valves, so this confuses me. Should it stay the same, drop or rise? lol

 

[bayellowstang]

I don't know about the rest of the stuff but normally they should be around 180 or so.

 

[UTGAMER]

Well it quit raining for a min and the next 2 were 125

 

[Chythar]

I've read folks here report anywhere between 120 and 150 and still be "OK". The main thing you're looking for is one cylinder with a significantly lower number than the rest. That tells you which cylinder has worn rings. We're talking more then 5-10 psi difference. The higher the overall numbers, the better.

As I remember, adding oil should either give you higher compression numbers or no change. If you get noticeably higher numbers, you're getting air & fuel pushing past the piston. In this case it usually means worn rings but can be other damage. No change with low psi can be valve seals but can be a damaged piston too. You'll need to complete the compression test before we can give you any definite ideas.

 

[UTGAMER]

I know was just bumed it was a 65-75 then happy it was 125. And it was raining so I though Id update. Now I just read that your supposed to only remove 1 spark plug at a time?

 

[HISSIN50]

It's best to have a hot motor. You can pull all the plugs at once. Connect a battery charger for equal cranking as you go. Disable the ignition and/or fuel system. Prop the throttle wide open. Then do the testing.

Did you ever do a cylinder-balance test while pulling codes? If one cylinder was not contributing properly, the test would have revealed it. It also makes it easier to pinpoint which cylinder(s) need attention.