Another XJ starting problem

[cherokeecrawler]

Haven't seen anybody post about there xj not wanting to start in awhile so mine thought it would be good to cause an issue about it. :doh:

1999 Jeep XJ sport. 4.0 /aw4. All stock except for a lift, tires and lockers.
I've actually had the issue for a little bit now, but can not seem to figure out with the issue is. I go to start it first thing in the morning and it turns over for a second then fires but after driving it and it's heat soaked, if you try to restart it, usually takes about 3 or 4 tries. Replaced the CPS with a mopar, already did a fuel pump almost a year ago now(same problem but it fixed it) so I don't think it would be that but just in case I got another free pump from a friend, not wanting to spend another $100 on a pump, he swore was good and came out of a 99 XJ. Started with a bump of the key when cold but after driving... same thing.
Would this be the fuel pump still? Also when it gets warm on the trail(200-210) it starts running real rough at crawl speeds(before I swapped the pump for the second time) would this be related?
At a total loss and I'm do to go on a wheeling trip in 2 weeks.
Any help is appreciated. Thanks.

 

[MiWiAu]

Do you have a fuel pressure gauge you can put on it? Should be able to get a basic one for <$30. AutoZone or Advance might even have a loaner you can borrow for free to confirm if fuel is your problem before you start throwing parts at it.

Any codes?

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[cherokeecrawler]

I don't but I'll try that. And the only code is for the lower o2 sensor.

 

[Lost_Wrench]

I'd definitely start with solving that check light and replacing your downstream O2 sensor.

If it's starting up cold and running fine I wouldn't think it to be your FP especially if you recently replaced it. Fuel filter been replaced in awhile?

 

[Saudade]

Heat soak can lead to a vapor lock in the later XJs. Lot's of threads in this and other forums on it.

 

[Czjeeper]

Have you done the TSB to heat wrap the injectors?

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[tech1001]

My XJ did the heat soak thing bad I made a heat shield that covers all the top of the intake manifold and the injectors goes though the heat shield and it stops the heat from getting to the injectors and fuel line .