hondohunter

Hello all,

I bought this 97 XJ 4.0, I relaced the cracked cylinder head on it.

Replaced the ignition coil, spark plug, and plug wires.

She starts up fine, but when I press the gas pedal all the way down she will misfire, pop, pop, pop, coming from the air intake.

I tested the fuel pressure and I am getting 5 psi with the key on, and 20psi with it running.

Surely I need a new fuel pump or something of the sort?

Thanks,

HH

tjwalker

Yea, 20 psi isn't going to cut it. The fuel pressure spec for your 1997 4.0 XJ is 49.2 plus or minus 5 psi. I always verify pressure with two gauges just to make sure. If you are actually at 20 psi, it is time to drop the tank and replace the entire "fuel pump assembly". It's been a while for me but I've always looked for Bosch assemblies, not sure if they are even available any more. I've also had decent look with Carter. Don't install an Airtex, I have had nothing but trouble with them and many threads on this and other XJ forums will give you lots of reading confirmation on this. Buy the best you can get.

Good luck and be sure to keep us updated!

bluejeep2001

Key on and running should be the same...before you drop tank replace fuel pump relay or jump out and verify 12v to the pump