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Re: low compression

To: "Eugene D Abbondelo" <>, <>
Subject: Re: low compression
From: "Eric J Russell" <>
Date: Wed, 25 May 2005 21:26:12 -0400
----- Original Message ----- 
From: "Eugene D Abbondelo"

> What happens when you drive a car with low compression in 1 cylinder?
> Will the engine eventually stop running or lock up without warning?

Probably not.

> Should I disconnect the spark plug lead from the bad cylinder and drive it
> like that, or leave it attached?

Hmm, not sure. Disconnecting it will lead to uncombusted fuel/air mix being
sent on into the exhaust system. I wonder if it'd combust in there. That
seems like a bad thing.

It might be worth rigging up a leak down tester to find out where/why the
compression is low. I've done this (cheaply) by screwing in a plastic hose
fitting (pipe threads on one side, hose barb on the other) into the spark
plug hole. Apply some compressed air with the piston at TDC then listen for
the leak. (be careful the engine doesn't suddenly turn)  If you hear hissing
in the tailpipe, likely the exhaust valve is burned, intake tract = intake
valve. Hissing from the oil fill opening is bad rings. Evidence of air in
the cooling system is either a cracked head or blown head gasket.

I guess the one to worry about the most (assuming you aren't going to fix
it) is leaks into the coolant system. The combustion gases will cause
problems and you'll have to watch the coolant level carefully & frequently.

Maybe if it's a blown head gasket it'd be worth fixing?

Eric Russell
Mebane, NC

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