1987xj with 4.0. 210k miles, been having backfiring issues. Did a compression test.

1. 135
2 155
3. 155
4. 155
5. 155
6. 145
Just curious what you guys think?

 

I like it! In my Sig, right on-top is a link to Cruisers tips. Highly recomend doing 1 through 5, (or #27 instead of #2)

 

Im on my phone,, Im not able to see signatures

 

Linky:
https://www.cherokeeforum.com/f23/te...itings-136452/

Backfiring out the exhaust or in the intake?

 

intakke

 

Might start with a fuel pressure check, could be a lean condition. Also check for damage to the ignition system, damaged fuel injector wiring, MAP problems, vacuum leaks..

 

I did check the fuel pressure and it was 28psi.

 

39# with the vacuum line off the regulator (on the front of the fuel rail), and about 10 less with it on.

Cruisers stuff will likely help you, in allot of ways. The sensors won't sense right if the grounds are not good, and the info won't make it to the puter' if the C-101 connector is crap. Then the CPS check...it's the "heartbeat", won't work well if that's funky!

 

That's too low.

What did it go to when you pulled the vacuum line off the fuel pressure regulator?

 

Didnt change.

 

Bad pump/clogged filter/busted rubber hose inside tank.

 

Yeah I've seen that rubber hose inside the tank cause problems.

 

What could make it backfire through the exhaust?

 

I think that is was Radi was getten at in post #6, being lean making it backfire. No ****! It never goes up to closer to 40?...looks like you guy's found the problem.

 

Running too rich is the most common, retarded timing, ignition system trouble or valve issues can do it too.