Compression test results

[jeepstertim]

Concerned about a lack of power in my 3.9 EFI defender i carried out a compression test yesterday and got reasdings from 130 - 140 across all cylinders which seem a bit down on what i was expecting.

While testing i also forgot to have the throttle full open, will this have affected my figures by much?

[katanaman]

It might have done but I dont think your figures are too bad anyway. They are all pretty close to each other so nothing major is happening.

[jefferybond]

While testing i also forgot to have the throttle full open, will this have affected my figures by much?

yes i believe that will make a difference.

jeff

[jeepstertim]

Which way is it likely to affect them, I am hoping they would be lower if the cylinder wasn't breathing so well - but by how much?

[katanaman]

if you did the test properly and turned the engine until the gauge stopped rising then there is no real difference throttle open or closed. I think the fact they are so close together means your testing was ok. Compression test isnt really the best as so many things can effect the result with ultimate reading. Leak down test is the ultimate but you need a compressor and a couple of other bits of kit to do that.