engine compression results Options

[LewFX]

I decided to try a engine compression. So i got a free loaner from autozone. got home. and the results are...

1: 150
2: 150
3: 135-140
4: 155

i know 150 is good, but what about the 135?

This post has been edited by LewFX: Mar 24, 2007 - 4:34 PM

[alltracman78]

Well, first off

Did you
have all 4 plugs out?
have the TB wide open?
Crank all 4 cyl the same amount of times [4 is recommended]?

The most important thing with a compression check is that all cylinders are close to the same number.
Usually 10 - 15 PSI difference is considered the limit.
What number you use depends on who you talk to, and how picky you want to be.

You can put a tablespoon of oil in the #3 cyl to see if the rings are worn.
If they are, the reading will come up considerably [it will come up some regardless].

If this yields nothing, you can either leave it as is, or do a leakdown test.
That's a bit more complicated, and you will need shop air. you can't just to it in your driveway with a gauge [unless you have an air compressor hooked up].
Doing this will tell you exactly where the cylinder is leaking from.

Keep in mind carbon buildup in the cyl can effect the readings also....

[LewFX]

Did you
have all 4 plugs out? no
have the TB wide open? no
Crank all 4 cyl the same amount of times [4 is recommended]? yes