Hello folks,

This is my first post here, but it's my first problem with my '91 Subaru 2.2 since I put it in my Vanagon. The 2.2 has 138k miles on it.

 

The other day I started it and had a tick-tick-tick-tick.

I did a compression check (cold) and had 200 psi in #4 and 100 psi in #2. That's 50 psi more in #4 than the last warm compression test I did and 50 psi less in #2.

I'm thinking the #2 is an honest cold compression.

This is my first problem with a Subaru engine and the first time I've ever had TOO much psi in a compression check.

Any ideas on what would cause more pressure in a cold compression check?

Thanks,

 

Rob

Hello folks,

This is my first post here, but it's my first problem with my '91 Subaru 2.2 since I put it in my Vanagon. The 2.2 has 138k miles on it.

 

The other day I started it and had a tick-tick-tick-tick.

I did a compression check (cold) and had 200 psi in #4 and 100 psi in #2. That's 50 psi more in #4 than the last warm compression test I did and 50 psi less in #2.

I'm thinking the #2 is an honest cold compression.

This is my first problem with a Subaru engine and the first time I've ever had TOO much psi in a compression check.

Any ideas on what would cause more pressure in a cold compression check?

Thanks,

 

Rob

 

just a idea; check the exhust cam or drop the exhust and listen for any air exiting the #4 cylinder. sounds like the exhust valves are not opening. like I said just an idea. good luck with it. D.

[...]I did a compression check (cold) and had 200 psi in #4 and 100 psi in #2. That's 50 psi more in #4 than the last warm compression test I did and 50 psi less in #2.

I'm thinking the #2 is an honest cold compression.[...]

It's not likely a closed exhaust valve (checking #4 for leakdown on what should be the exhaust stroke for that cylinder would easily determine that), although that would effectively give you twice as many "compression" strokes as usual. Cranking a sufficient number of revolutions when checking compression would even the readings if that's what's happening. EDIT: I believe that the '91 had hydraulic lifters, so one that wasn't pumping up could cause an exhaust valve problem, and explain the noise as well.

 

Perhaps you're doing an unintentional "wet" test. Can you peek/probe into #4's plug hole and see if it's got some fluid in there?

 

By the way, temporarily disabling the air-hold valve on a compression tester can sometimes be revealing. So can using a vacuum gauge, often even at cranking speed; of course, the spark plugs have to be in for that .

EDIT: I believe that the '91 had hydraulic lifters, so one that wasn't pumping up could cause an exhaust valve problem, and explain the noise as well.

 

That's what it was, one lifter had lost it's prime. Looking at the rockers it was the upper right lifter.

Thanks,

 

Rob

Did you do a compression teste with all the spark plugs out? If you have multiple sunk lifters i would check your oil pressure.

 

nipper

When you do a compression test, don't forget to disconnect the fuel pump too, not just the ignition coil.

 

Overcompression is a possibility, excessive carbon buildup can cause that.

When you do a compression test, don't forget to disconnect the fuel pump too, not just the ignition coil.

 

Overcompression is a possibility, excessive carbon buildup can cause that.

 

Yes, but i was more concerned about the 200/50 split. That shows a few other nasty problems aside from lifters.

 

Did you do a wet comperssion test too?

 

nipper

EDIT: I believe that the '91 had hydraulic lifters, so one that wasn't pumping up could cause an exhaust valve problem, and explain the noise as well.

 

That's what it was, one lifter had lost it's prime. Looking at the rockers it was the upper right lifter.

Thanks,

 

Rob

You're welcome. Excessive lifter leak-down can be caused by several things. Engine oil that's dirty, fuel-contaminated, wrong viscosity, aerated, or just not getting where it needs to can all cause the problem, although those things tend to affect more than one lifter. If the oil hasn't been changed in a while, doing so might be a good idea.

 

Sludge and/or varnish can be a cause, and of course, a damaged/worn lifter is also a possibility.

 

If an engine isn't run for a long enough period, a marginal lifter can leak down while the others hold. Even good lifters leak down after sitting unused for long enough, and which ones will be more prone to do so can depend on the rotational position at which the engine has stopped; pressure on a particular lifter will vary with the point in each cylinder's cycle (percentage of cam lift). If things are okay, they'll pump up again within seconds to maybe a minute or so.

 

EDIT: See the sections concerning HLAs (Hydraulic Lash Assemblies) and how rocker shaft relief valves can affect them in http://www.endwrench.com/pdf/engine/FtEngineOverhaulSp98.pdf .

I came across this thread, which might be of interest: http://www.ultimatesubaru.org/forum/showthread.php?t=47262