I just pulled a k24a2 from a junkyard, and wanted to check compression numbers to see if I needed to rebuild it or not.

Motor cranked over fine, and the timing change seemed tight, so we jumped the starter and our first set of numbers:

130-150-150-90

We did it again and we got:

90-30-150-130

Tried it one more time and we got:

120-75-150-130

I did test cylinder 2 multiple times, the first time I got 30, I got it 3 times in a row, did all cylinders again and then it jumped up to 60 with no change, then 75.

This is the first time I ever did a compression test outside of the vehicle, so I wanted to see if anyone had any input on why this would happen.

A couple of theorys I had is that the chain could of skipped a tooth and is allowing air to escape. Or the motor could've been sitting a while and something could've helped hold pressure in the rings maybe.

I just kinda wanted some ideas before I tear into it if I don't have to.

Thanks

 

Check the mechanical timing marks to make sure the engine hasn't jumped time. If it has, you cannot rely on the compression numbers. Also, you must be able to spin over the engine at 250 rpm or faster to get proper compression results... turning slower skews the compression numbers and lower values are the result.

 

That was kinda what I was thinking since the numbers kept changing. I'm heading back over this weekend, so we will check timing, honestly something I should've done before we even tried to crank it but I figured because I could spin it over by hand in the yard and it only had 143,000 miles on it, I assumed it was fine. Will update by Sunday.

Thanks