Compression Check
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Compression Check
I did a compression check on my 1990 Ranger 4x4 2.9L V-6. Five of the cylinders registered the same. No. 3 didn't register any compression. Now, do I need a valve job or possibly a re-ring job. The truck doesn't use oil and doesn't smoke any. It doesn't have any power going up the mountain where I live and the gas mileage went way down. Any help appreciated....Thanks!
Post Fiend
Joined: Feb 2003
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From: Eastern WA
No compression as in zero? It would take severly worn or maybe broken rings, a hole in a piston, or a major burnt valve to do that; I've never seen a case of zero compression on one cylinder. I would also be wondering if a valve is stuck open a bit; enough to cause a major compression loss yet not enough to make contact with the piston ( 
). In your case with no oil consumption, I'm thinking valve issues.
Did the problem come up all at once or was it gradual and over time? Is there the sound of rushing air in the exhaust or at the intake indicating a bad valve and thus creating the noise? What did the plug on the dead cylinder look like? Any chance you didn't do a good test on the dead cylinder?
). In your case with no oil consumption, I'm thinking valve issues. Did the problem come up all at once or was it gradual and over time? Is there the sound of rushing air in the exhaust or at the intake indicating a bad valve and thus creating the noise? What did the plug on the dead cylinder look like? Any chance you didn't do a good test on the dead cylinder?
Fleet Mechanic
Joined: Dec 2003
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From: Virginia
Originally Posted by CowboyBilly9Mile
In your case with no oil consumption, I'm thinking valve issues.
Seriously, a stuck/bent valve is your best bet.
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Compression Check Reply
Bill, thanks for your response. The problem has been gradual over a short period. I did the test three times....it would register a little, but not enough compared to the other cylinders. It was not completely zero! I did have a blown head gasket about 6 months ago, which I repaired. Thanks again!
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