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-   -   Intermittant total compression loss? (http://www.diychatroom.com/f46/intermittant-total-compression-loss-19095/)

johnd393 03-27-2008 03:27 PM

Intermittant total compression loss?
 
The car is a 96 Geo Metro 3 cyl with 190000 miles.
Sometimes it will crank and run normally. Other times the engine cranks like it is spinning freely like all the plugs were out. Like zero compression. It has got worse to where it will start and die and than spin like no compression until it's left to sit for a while. Sometimes it will sound like compression on one cylinder for a few seconds. Than, after sitting maybe 1/2 hour, the compression comes back normal just long enough for it to start and die again. The timing belt is fine and has not slipped. I thought maybe a lifter problem. If the valves were intermittently not closing I think I would hear some sound from it. If the valves were not opening, wouldn't there still be some compression? This seems impossible. I'm replacing the motor cus it also has a bad knock, but I can't see how it can do what it's doing.
John D

slickshift 03-27-2008 03:29 PM

Feels/sounds "like" no compression, or actual compression tests zero or low on a during this no start condition

There is a huge difference

How do you know the timing belt is fine?

johnd393 03-27-2008 03:47 PM

No compression test was done. You know what a free spinning engine with no, or very little, compression sounds like from the sound, don't you?

I physically inspected the timing belt and it's alignment.

John

slickshift 03-27-2008 04:04 PM

Quote:

Originally Posted by johnd393
You know what a free spinning engine with no, or very little, compression sounds like from the sound, don't you?

Well, yes....it does have a sort of sound thing going on
But it really doesn't mean anything...it could be other things also
It's a suspicion, it's not conclusive by any means
Its certainly not enough to consider it a compression problem w/o an actual test
You need to do the test and find out if it's actually a compression problem
In reality, as far as we know at this point, you may have plenty of compression

You also need to do a timing test while it's running
I know you looked at it, but that doesn't tell us if the timing is actually wacked when it's running

johnd393 03-27-2008 04:35 PM

The only way it could make that free spinning cranking sound is loss of compression unless the stater is not actually spinning the engine. It almost sounds like the starter spinning freely. First time it happened, I had my wife crank it while I looked to see if the engine was actually turning. I also into the oil filler hole at the cam to make sure it was actually turning and it is. We thought we were stranded but in a few minutes it started and ran fine all the way home. You can't check the timing belt while running. I suppose I could have checked the ignition timing. I've already started taking it apart to replace the engine. Most of the wiring is disconnected. It's too late to do any more testing. I may take it apart to see it I can see whats wrong. I have another motor that I bought from some guy that had it rebuilt and never installed it.

mbad7 03-28-2008 11:52 AM

Quote:

Originally Posted by johnd393 (Post 111408)
The car is a 96 Geo Metro 3 cyl with 190000 miles.
Sometimes it will crank and run normally. Other times the engine cranks like it is spinning freely like all the plugs were out. Like zero compression. It has got worse to where it will start and die and than spin like no compression until it's left to sit for a while. Sometimes it will sound like compression on one cylinder for a few seconds. Than, after sitting maybe 1/2 hour, the compression comes back normal just long enough for it to start and die again. The timing belt is fine and has not slipped. I thought maybe a lifter problem. If the valves were intermittently not closing I think I would hear some sound from it. If the valves were not opening, wouldn't there still be some compression? This seems impossible. I'm replacing the motor cus it also has a bad knock, but I can't see how it can do what it's doing.
John D

Had the same symptoms with a Lancia over here in Europe! Turned out that the valves were open all the time,just enough to let te compression out,but not enough to touch the pistons... New valve pads,and a tune up solved the problem... Hope this helps:)


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