Compression test results
 

My Jeep has never seemed to have the power that my friends 4.0L jeeps do. Did a compression test today for the hell of it, this is what i found.

Im not sure what it "should" be, so my question I guess would be How does it look?

http://farm8.staticflickr.com/7025/6...b0522b15_z.jpg

Wow, my renix at 250000+ km was 140psi on all six...

This one has only 220,000 kilometers (136,000 miles)

Leak down test?

The only thing significant about those numbers is cyl #5......it's headed south. The range/variance of the numbers hi/low should be less than 10%.

Did you do this test with the engine hot or cold because that will affect the numbers.

Correct way to do a compression test is with the motor warm, all spark plugs removed and throttle held wide open while starter motor is cranked.

engine was cold.

And - make sure each cylinder gets an equal number of pulses.

Watch while it pulses - at least 90% of the final value should happen with the first pulse.
95-96% on the second pulse.
Max pulses should be 4.

Some people crank and crank till they get what they want - totally invalid!

How do they "get what they want"?:confused:

I like 7. Just seems thorough. X2, warm, leak-down, 10%. What year? Is yours really doggen or are they just louder? If you are sure everything is right and it's doggen, once I had a clogged cat do that. Finally I loosened the bolts on the header pipe on (her "K" car), and WOW, night and day, that was it.

I'm still puzzled about 140 psi on all six......seems physically impossible.:sweatdrop: Leak down and compression test are 2 different animals.

??? "Leakdown" is the term I've always used for "wet", a few tablespoons of oil in there. Admittedly that doesn't sound right.

Well...just googled it, I stand corrected. Done with compressed air.....

#5 is a bit off but overall there's nothing wrong with these numbers for a 4.0 XJ

What should the ideal or target compression numbers be for a 97 4.0?

Flash