Engine compression testing

[ponkotsu]

Bought a new compression tester today and tested my 4.6L Aviator. Pulled all the plugs out and had the wife crank the engine. I tested cylinders 1-4 and all maxed out between 160-170psi. That is good compression, but what I'm concerned about is the amount of time it took. I thought it would take 3 compression strokes to get full pressure. But mine took much longer. First stroke about 50-60psi, then 80, 100, 110, 120, something like that. Anyone have a similar experience? Seems like the engine is not building pressure like it should.

 

[Albino 94LTD]

A better question might be, is it holding pressure once it is built up?

But I agree, I would think it should build pressure pretty quick, even with the added volume hose and gauge (unless you have a really long hose).

That was a dry test (no injectors shooting a fuel mixture into the cavity which will take up a minimal amount of volume but won't compress).

How fast does it build if you shoot a quick shot of WD40 in before hooking up the gauge?

 

[ponkotsu]

A better question might be, is it holding pressure once it is built up?

But I agree, I would think it should build pressure pretty quick, even with the added volume hose and gauge (unless you have a really long hose).

That was a dry test (no injectors shooting a fuel mixture into the cavity which will take up a minimal amount of volume but won't compress).

How fast does it build if you shoot a quick shot of WD40 in before hooking up the gauge?

I dropped a little motor oil in the cylinder and it seemed to build up just a bit faster. I don't think I put enough in though, and the cylinders are angled so I doubt if it got onto most of the ring. It's a HF gage that I saw others use on youtube and the pressure went up real quick. I did have an issue with the intake being badly gummed up so it looks like ring blow by for sure. I'm considering doing a cylinder soak with something but that is a little risky.

 

[colintrax]

Just curious you were holding the throttle wide open right?

 

[ponkotsu]

Just curious you were holding the throttle wide open right?

Yes