Weird Result From Compression Test. - BMW Forum - BimmerWerkz.com
3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

 
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#1 (permalink) Old 04-15-2005, 10:00 PM
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So I bought a parts car yesterday for $340.00. It ran for a bit so I know it runs.
I pull the main fuse, pull all the spark plugs, thread in the tester, push the peddle all the way down and turn the car over. The result....cranking but absolutely no compression to the #1 cylinder. I mean none. I do however get a gas smell.
I would just worry that the #1 cylinder is totaly shot but I just did the same exact commression test to my other E-30 right before this. I'm a bit lost as to why the first car has a gas smell and the second didn't at all. And why there would be no commpression to the cylinder.
Thanks in advance.

Finally pulled the M50 from the donor car.
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#2 (permalink) Old 04-15-2005, 10:13 PM
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Quote:
Originally posted by joshh@Apr 15 2005, 10:00 PM
So I bought a parts car yesterday for $340.00. It ran for a bit so I know it runs.
I pull the main fuse, pull all the spark plugs, thread in the tester, push the peddle all the way down and turn the car over. The result....cranking but absolutely no compression to the #1 cylinder. I mean none. I do however get a gas smell.
I would just worry that the #1 cylinder is totaly shot but I just did the same exact commression test to my other E-30 right before this. I'm a bit lost as to why the first car has a gas smell and the second didn't at all. And why there would be no commpression to the cylinder.
I even had my daughter look and make sure the belt wasn't just slipping on the pully.

Thanks in advance.
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Perhaps the timing belt slipped a tooth?? How does it run, is it like "skipping" when it runs?
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#3 (permalink) Old 04-15-2005, 11:06 PM
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Even if it skipped I tooth, I would think there would still be compression. 2 teeth off is fine with this motor. 3 teeth = valve damage.

Finally pulled the M50 from the donor car.
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#4 (permalink) Old 04-16-2005, 09:24 PM
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If anyone cares heres what I found.......

I remember reading in the Bentley that the older cam gears were recalled and replaced with stronger ones. Well by the looks of this one compared to the one on my other E-30, this is the old cam gear.
Well the cam gear had broke at the base and was just spinning without turning the cam. So the bottom end was turning and the head was not.
The result....at least 2 bent valves.
Just a warning to all you without the newer cam gear.

Finally pulled the M50 from the donor car.
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