General Compression testing

[YSporting2003]

I’ve just done a comparison test on my 1.2 16v.
Results were 225psi for cylinder 1&3 203psi for cylinder 3&4. Was just wondering what the compression should be so I know that mines are within that range thanks.

 

[ZaphodB]

I don't know what the figures for your engine are, but as much as it's about the pressure, what's absolutely important in the difference between cylinders.

Give the starter motor a rest and do the test again on all to make sure you've got solid figures.

 

[Mike1alike]

Compression should be above 100 psi for the cylinder to fire (but that is a bad value).
175 psi and above is good compression.
The difference between cylinders should not be more than 20% between higher and lower.
This is for petrol engines, I don't know if for diesel is different.