F-134 Compresion

This was posted by someone here (can't remember who ) a few years back, I saved it as Good Information-

When performing a compression test, your be looking at variations "within" each cylinder and also "across" all
cylinders..

A: Do the test AFTER the engine has been run at normal operating temp.

B: Per cylinder, record the first and 4th stroke of the needle on the compression guage
(you have to look at the guage for the 1st stroke of the needle...
the needle on the guage will stay on the 4th stroke until you release the valve on the guage).



The readings...

Typically want less than a 10% variation "within" and "across" the cylinders. Service manual will tell you want
compression should be within the cylinder (believe less than 80 is typically not good)

Within each cylinder, if the first stroke is more than 10psi lower than the last/4th stroke, add oil to the
cylinder and retry. If the 1st stroke is better on the retest, there's typically a ring issue. If no change, look
for valve issues.

If readings are low and identical on two cylinders next to each other, check for head gasket issues.

A vacuum guage is also good for checking the engines health (when running) as is a cylinder leak down test.


H.