Help with 2F Compression Test Results (FJ40) (1 Viewer)

[rstoddard]

I performed a Compression Test on my ‘78 FJ40 today and got what I think are some concerning results:

#1 149
#2 129
#3 125
#4 129
#5 130
#6 149

So, what do the the readings of 130 indicate versus the higher readings of 149? That about 13% lower. Then there is the 125 reading (which I tested twice and confirmed)?

Do these just suggest bad valves or rings or does this suggest a bad head gasket?

Is there anything I can/should do at this point to try to isolate what the problem is and what action I might need to take?

TIA for the advice!

 

[rkymtnflyfisher]

I'd start with a valve adjustment, then check comp numbers again.

 

[rkymtnflyfisher]

Those numbers aren't really that bad, no reason to be too concerned. Yeah they may be out of spec based on the FSM, but after 45 years it's not worth losing much sleep over.

 

[POTATO LAUNCHER]

I'll second a valve adjustment. I don't see a huge concern with those compression numbers.

 

[fjc-man]

What are you trying to “narrow down” is there a problem?

 

[fyton2v]

Was the engine warm? I had somewhat worse numbers with properly set valves clearances when it was cold. Then I ran a bunch of seafoam through the carb, drove it fast for about 100 miles and then saw very different results when good and warm.

 

[rstoddard]

The engine was warm, and I did a valve adjustment a couple weeks ago. I checked them 2-3 times to be sure the were right.

 

[rstoddard]

What are you trying to “narrow down” is there a problem?

I was have some white smoke on start-up on a couple of occasions after the vehicle has been sitting, most recently the other day. That was about a week after I had washed the car at the car wash with a high pressure hose wand and sprayed in the engine compartment to clean out some oil and coolant that spilled.

I think that some moisture may have gotten into the intake. Maybe I have a leak in the manifold? It didn’t smoke the next day, so I don’t know what to think. I thought I would test the compression to see if it indicated a head gasket problem.

 

[POTATO LAUNCHER]

Your plugs didn't show any major concerns. Check the torque on the intake/ exhaust manifold. High pressure could have forced water in but its not a big deal once you get it up to temperature and it exits the exhaust.
Other than decent compression numbers are you experiencing any idle/power issues?
It is a 45 year old tractor engine with unknown history unless you bought it new. I would not over think the minor details too much.
You seem to have an understanding of the mechanics, keep the oil changed, radiator full, carb adjusted properly and don't over rev it. The O'l 2F should give you many more miles of dependable service.
Casey...

 

[WildernessRimFab]

I was have some white smoke on start-up on a couple of occasions after the vehicle has been sitting, most recently the other day.

White smoke on startup is a symptom of worn out valve stem seals.

 

[fyton2v]

If the smoke is damp it's probably just condensation turning to steam.

 

[rstoddard]

Your plugs didn't show any major concerns. Check the torque on the intake/ exhaust manifold. High pressure could have forced water in but its not a big deal once you get it up to temperature and it exits the exhaust.
Other than decent compression numbers are you experiencing any idle/power issues?
It is a 45 year old tractor engine with unknown history unless you bought it new. I would not over think the minor details too much.
You seem to have an understanding of the mechanics, keep the oil changed, radiator full, carb adjusted properly and don't over rev it. The O'l 2F should give you many more miles of dependable service.
Casey...

No power issues. I had it out on the highway and it climbed to 70-75 mph without me realizing it or even pushing it. It idles decent, although I was going to have Jim C do a tune up on the Carb.

 

[pjohnson]

Try a wet compression test and see if you get a similar spread. It seems like normal wear from what you have described so far.

 

[rstoddard]

Try a wet compression test and see if you get a similar spread. It seems like normal wear from what you have described so far.

How much oil do you use for a wet test?

 

[fjc-man]

A couple three handheld oil can pumps.

 

[rstoddard]

A couple three handheld oil can pumps.

@pjohnson
So, I performed a wet compression test today and got some pretty interesting results:

Dry. Wet
#1 149. 151
#2 129. 145
#3 125. 142
#4 129. 146
#5 130. 145
#6 149. 156

So, does this just indicate normal ring & cylinder wear on 2-5?

 

[pjohnson]

@rstoddard
That would my conclusion. You're wet numbers are great and within a 14psi range.