99Chilipeppercherokee

Hello. I recently bought a 99 xj. The vehicle itself isn't stock but the engine side is all stock so I'm posting it here. Hopefully that's alright. Anyhow, the problem I am having is a hard start after it has been sitting for more than a couple hours. If I don't give it throttle it stumbles to life, but when I give it throttle it starts clean. Still cranks for a while though. If I shut it off and start it again it starts pretty much first crank. I know that the first suspect is fuel pressure so I tested it out and at idle it was 55 and 5 mins after I shut it off it was 50, after 15 mins it was about 38, and after 30 it was around 22. After sitting til no pressure it primes to 45-50 and then quickly drops to about 40 and then slowly lowers from there. That seems about right from what I have read. The poor man's prime doesn't help either. I also scanned for codes and all that popped up was TPS low voltage which I figured would probably be the problem so I replaced the TPS with a Mopar one because the old one was a POS. Obviously that hasn't fixed it otherwise I wouldn't be posting this. I haven't checked to see if the code is gone but not sure what else would fix it. No check engine lights either and it does illuminate. I also looked at the throttle body and it has a light coating on it but looks like it has been cleaned relatively recently. Not sure if it's relevant but it has a slightly rough idle when it's first started and it persists until it's about at operating temp and then it runs flawless. At this point I'm not sure what the problem is so any suggestions would be appreciated. Thank you!

Dave51

Replace pressure regulator on top of fuel tank.

How are you doing "poor man's prime"?

DON"T get this pressure regulator:

99Chilipeppercherokee

Thanks for the reply. Not that I don't believe the fuel pressure regulator will fix the problem but I am just curious how you came to that solution.
For the poor man's prime, I turn the key to run, let the fuel pump run until it stops, and then wait a sec and do it again.

Dave51

Read it on the internet somewhere.

Dave51

https://naxja.org/threads/fuel-pump-...valve.1102760/

If you want to do the fuel pump it's BOSCH 67658 Fuel Pump Module Assembly but TTBOMK you can't get one.

I have no recommendations for reliable alternatives.

Get new J-bolts. It's a quick job with bolt cutters.

Dave51

I did cut my OEM one up, didn't take pictures of the springs tho. Forgot why:



That's all I got...