Thread: low compression
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Old 04-05-2002, 07:33 PM
tcane tcane is offline
Senior Member
Join Date: Jul 2001
Location: San Antone
Posts: 408
Cold compression of 120 psi is really low, 130 psi at sea level is about the minimum for the engine to start and run, as you gain altitude the compression psi goes down (take the engine's compression ratio X atmospheric pressure at the altitude where you're located - say 9 to 1 compression ratio and sea level with about 14.5 psi atmospheric pressure: 9 x 14.5 = 130.5 psi for minimum compression for an engine to work - this is just a rule of thumb and not specific to any engine). 150 psi cold compression or higher is closer to what you should have and 175 + psi hot. If the plugs are wet then it could either be not enough compression, too much fuel, fuel timing to the nozzles is wrong, the ignition timing is off (there could be other problems like the timing chain has jumped a tooth, bent valves, bad head gasket, weak coil(s), distributor is not timed to the engine correctly, etc., etc.). I am throwing out some ideas as to why your engine won't start since I don't own your model, but past experience with many other vehicles suggests my list as some of the reasons why you're having problems.

Try this, squirt a little oil into the cylinder, connect your compression gauge to that cylinder, and spin the engine to see what the reading is. If the compression remains the same with oil then the valves are suspect and if the compression goes up then the rings are bad. If the valves are bad then you can pressurize the cylinder and then listen to see which valve leaks - use a stethoscope, a screw driver, a piece of wood (like a cut off broom handle), or perhaps just your ear to listen for where air is escaping - out the exhaust pipe is a bad exhaust valve and out the intake/air cleaner is a bad intake valve, and a bad head gasket can have bubbles/air escaping out the radiator.

Perhaps another member or a moderator has the "silver bullet" fix for your problem - like something in the electronic control system.

Good Luck!
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Last edited by tcane; 04-05-2002 at 07:55 PM.
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