High compression in one cylinder

[debaron]

Chaps, need to work what might be causing high compression in one cylinder.

Results are all pretty good with the exception of cylinder 6 which is reading 20psi higher than the rest. Oddly it has the highest leak down of all...


1 205 psi 10% leak down
2 205 psi 16% leak down
3 200 psi 13% leak down
4 200 psi 7% leak down
5 200 psi 13% leak down
6 220 psi 18% leak down
7 199 psi 16% leak down
8 200 psi 16% leak down

Any ideas?

thanks

[debaron]

phazed said:

It is a possibility that your leak down test was not accurate.

Could well be - it was £30 off Amazon and had a Schrader valve in the pipe which needed removing before it would work!

[debaron]

If those leak down values were right, surely I'd be getting loads of blow-by??

[debaron]

Bluebottle said:

Whilst carrying out the leak down test, with leakage that high (if gauge accurate) you should have been able to hear where the air was leaking? Did you go around the engine with an engineers stethoscope to listen for air escaping either into the exhaust system or into the sump (past the rings)?

Yes - all air leaking was heard in oil filler cap - which is normal for leaking past rings I think.