11 replies to this topic

[Lsurt95]

hi

 

Recently my engine has been running quite poor. I took the Spark plugs out to discover number 4 was damp and almost oily. I then decided to do a compression test and come across an unusual reading (these were done while cold)

 

cylinder 4- 225 psi 

 

cylinder 3- 175 psi 

 

cylinder 2- 175 psi

 

cylinder 1- 175psi

 

has anyone got a possible reason for this?

 

Thanks

 

Liam

[Fast Ivan]

I've read in one of the manuals, forget which one, that it could be carbon build up in the combustion chamber, so head off and clean being the solution. I would do if hot first though with the throttle open

[ANON]

knackered oil rings.do a leak down test though, compression test doesn't really tell you anything.

Edited by ANON, 27 September 2014 - 04:56 PM.

[Fast Ivan]

A compression test doesn't tell you anything? Yet you've determined that the oil rings are knackered, how have you managed that?

[Dusky]

Oil makes of a wet compression test = higher readings

[ANON]

A compression test doesn't tell you anything? Yet you've determined that the oil rings are knackered, how have you managed that?

 

 

by knowing what i'm talking about  dusky is cleva as well!!

[carbon]

+1 for Rob Mac's suggestion.

 

If you have a significant build up of coke on the piston and cylinder head this will raise the compression. Fits with the sparking plug on number 4 cylinder being oily.

[ANON]

isn't carbon build up generally caused by oil getting past the rings? 

[cal844]

isn't carbon build up generally caused by oil getting past the rings?

Yes or too rich mix

[Rog46]

OK time to own up to my ignorance. Can you describe a leak down test please?

[gazza82]

http://www.wcenginee...s/leakdown.html

[Rog46]

Thanks, looks and sounds beyond most of us without the special kit, though I'm wondering what you could do with a compressor and a flow gauge.