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In cylinder compression results

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10 Mar 2019 13:03 #27720 by DIYGUY
In cylinder compression results was created by DIYGUY
I recently bought a car and had checked the compression on the engine using a regular compression gauge. This engine is a 3 cylinder. # 1 and # 3 cylinder were right around 200 psi. The # 2 cylinder was at 100 psi. I tested the engine in a few different ways to see if I could diagnois what the cause of the low compression was.

A leak down test was done and the gauge showed a 50% lose and the air leak was most evident through the exhaust pipe. I also did a in cylinder compression test on cylinder # 1 and # 2 while cranking the engine over. Below are those graphs .

There is a noticeable difference in the compression reading, just as the results on the mechanical gauge showed. There is also a noticeable difference on the waveform at the end of the power stroke. It is deeper and appears to last a little longer. Is that normal, and would that be something to look for when suspecting a valve issue? The head had been removed and the # 2 cylinder has a burnt exhaust valve.

Cylinder # 1
https://flic.kr/p/24vMUgK

Cylinder # 2
https://flic.kr/p/24vMULH



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10 Mar 2019 13:50 #27724 by Andy.MacFadyen
Replied by Andy.MacFadyen on topic In cylinder compression results
It is without question an exhaust valve issue it could be a lack of valve clearance but more likely a burnt or bent valve.

"There's always a catch ---- Catch OBD2 ."


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10 Mar 2019 16:17 #27727 by DIYGUY
Replied by DIYGUY on topic In cylinder compression results
I just got the head off this morning and the valve was burnt.

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