A couple of weeks ago I had a couple of misfire codes show up, but I cleared them and they haven't reappeared. The first was random misfires and the second (pending) was for cylinder 2. I finally got around to doing a compression check and got the following in this order:

dry:
1 137
2 104 (yikes)
3 117
(2) 114 (had to try again; looks a little better)
4 122

wet:
1 130 (???)
2 125
3 135
4 130

1 120 (now dry (more or less) but I like the initial 137 much better)

So I'm doing something wrong or my gauge is wacked; and the big question is what is (not) happening?

I don't have much trust in the absolute numbers but I wouldn't expect the gauge to be so inconsistent.

When I removed the spark plug for 2, it was covered in oil but it appeared to be on the tube side only. 3 had some oil sludge on the top side but not nearly as much. All tips looked similar and reasonable for 73k miles.

I was watching the gauge as someone cranked the engine, so I could see the pressure increase and level off. Its not as if cranking stopped to early or the gauge leaked before I could read it. The gauge itself is a cheapo from Sears of 20+ years ago. Maybe the valve is bad?

Any tips on getting better measurements would be greatly appreciated.

 

My mantra is that if you can’t absolutely trust your gauges, get rid of them.

But in this case a compression gauge is simple. The Schrader valve core has a bit of rubber on it and clearly after 20 years it is probably compromised.

I would do the test again with a newer borrowed gauge and post the newer results.

///Rich

 

Thanks. Makes sense. I think I was slowly coming to that conclusion as I was composing that post.

Anyone care to recommend brands (to avoid or to praise)? Doesn't seem like it should matter much as long as the valve and dial aren't sticky