AMXJ

Anyone have any ideas on this one? This is a 91 XJ 4.0L Auto trans. daily driver.

The problem started last week, when I started my Jeep to go home from work. The Jeep cranked longer than normal and when it started it popped and sputtered and died. Started it again and it did the same thing. The third or forth time it started it ran fine and I drove home without any problem. The next morning when I started the Jeep it did the same popping, sputtering, and died a couple of times. It had been a while since I had replaced my fuel filter so I went ahead replaced it. I started the Jeep and it ran fine. It's been running fine all week until yesterday when I was leaving work it did the same popping, sputtering, etc. right after starting. I kept one foot on the brake and one on the throttle and started driving home. As soon as it warmed up a bit it stopped having issues and ran fine again. This morning it went back to popping, stalling, Etc. after starting so I left it at home today.

Anyone have any ideas of common things to check that might cause this???

Thanks
Dennis

PatHenry

I'd do the standard grounds cleaning and then check the fuel pressure. Does it seem like it's not getting gas?

You might also want to clean your IAC motor and throttle body.

tjwalker

Any check engine light on? If so must pull codes.

Agree with PatHenry, fuel is definitely high on the suspect list here. For your 91, you should have about 31 psi at idle. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi.

If you don't have access to a fuel pressure gauge, you can usually rent a kit inexpensively from local parts stores; call around for availability.

Do that and report back what you find!

AMXJ

Thank you guys!!
I checked the fuel pressure both with and without the vacuum line attached to the regulator but was getting inconsistent pressure readings almost every time. First it would check out good then test it again and pressure is lower than it should be.

I replaced the fuel pump/sending unit with a new Delphi unit from Summit Racing and it seems to be running fine now. While I was under the Jeep I noticed that the plug on the CPS wire had melted a bit from being too close the header so I replaced the CPS as well. So I'm not really sure which of these actually fixed the problem, but it is fixed and runs great again.

Thanks again for the suggestions guys!!
Dennis

aa7kn

I would think your fuel pump was your problem. You said you had changing pressure readings. It is a good idea to change the melted connector you mentioned. But I think it was the fuel pump that actually fixed you problem. Glad you got it fixed.