compression testing 2000 v70

[famfeld]

It occurred to me to do a compression check on my engine before embarking on the next several projects. Here are my results:

Cyl 1: 120
Cyl 2: 180
Cyl 3: 180
Cyl 4: 150
Cyl 5: 170

I just paid to have this salvage yard motor installed in my car and was curious on how the compression was. Is this acceptable?

Any opinions appreciated.

Thanks,

-Feld

[bmdubya1198]

From what I've read, 120 PSI is good. It seems weird to me that you have between 150 and 180 on the rest of the cylinders, but apparently anything between 120-180 PSI is good on these engines. I wouldn't be concerned unless it's under 110-115.

[famfeld]

Thanks. Just working on the car and posting all my questions today!

[tryingbe]

Did you test the engine cold or warm?

[erikv11]

Yeah, if the engine was warm, that spread (120 to 180) is not so good. If the salvage engine has barely been run then give it 50 miles and check again.

If the engine wasn't warm then warm it up, pull the fuel pump fuse and/or floor the pedal, and get a fresh set of numbers.

Presumably this is a low pressure turbo engine?

[j-dawg]

The most important thing is that all the cylinders be close to one another. Other variables - starter condition, temperature, the tester you're using, etc - can affect what that number actually is, but a cylinder being a significant outlier - or all your compression numbers being very low - suggests that there's something wrong. That 120 is looking pretty dodgy, and the 150 is on the low end too.

[erikv11]

Yes, the troubling issue is the spread (120 to 180), if that spread came from a meaningful compression test.

However we need more info about how the test was done to say much of anything at all. If the test wasn't meaningful (e.g. see below), then the numbers certainly aren't either.

Testing the compression cold gives some information true, but that info is not very relevant to how the engine performs driving down the road. Temperature certainly matters, just do it right. Similarly, was the throttle wide open as it must be? Etc.

The engine came from a junkyard so it also matters (a lot) how long the engine sat before installation, and how much it has been run since installation. Think of a sticky piston ring or valve.

[bmdubya1198]

Yeah, I thought the 120 seemed off. When I was reading around yesterday, I saw someone mention that 120 was perfectly acceptable, but it still seems low to me. Like I said in my first reply, the spread is what concerns me.
And I'll repeat what has already been said, the compression test needs to be done on a warm engine, fuel pump relay removed, throttle held wide open. And, of course, performed with a good, working gauge. That will give you the most accurate reading.

[famfeld]

I did disconnect the fuel pump relay, didn't open the throttle body. The motor was relatively cold. I'll retry it warm. Thanks
Feld

[j-dawg]

Dribble a teaspoon of oil into the low cylinders and try again. A dramatic improvement in those cylinders' results would indicate worn piston rings, which is a more costly repair than, for example, a head gasket.