Good Morning,

I just got a 1993 Jeep Cherokee 2WD 4.0L, my problem is that after driving 10-15 min my truck suddenly turns off, the fuel pump was making a lot of noise so I replaced, but it keeps doing the same sound and still after a 10 min drive it turns on & off like missing fuel, I went to autozone and rent the fuel pressure test and plugged into the fuel injector rail, when I open the key it reads 10 psi, turn on the engine for 10 min and constantly reads 35 psi, turn off the engine and after sitting 10 min goes to 12 psi. Any ideas of what can be the problem? Does anyone knows the PSI specs for this model? I have a 2000 XJ 4X4 and reads 45 psi with the engine on, it has to be the same pressure on both? Thanks

 

A 94 (which should be similar) is 31psi at idle, then if you pull the vacuum line off the pressure regulator it should jump to 39psi. It can drop 20psi (so 11psi) within 30 minutes when the engine is off.
So it sounds like the pump is operating within specs unless there was a major part difference between 93 and 94.

So is the new pump noisy? Did you replace the entire assembly or just the actual pump?

Perhaps someone with more expertise can jump in and advise.

 

Thanks for your answer, I was looking into the forum and found that it can that the fuel pump ballast resistor is bad, but when I looked under my hood the 2 wires next to the ballast seem like jumped, maybe that can be the issue? also read that the ballast function is to shut down the noise of the fuel pump, I replaced the entire assembly of the fuel pump!

 

If your new fuel pump is truly noisy, it is possible that you got a bad one from the parts store.

But also remember that on your vintage, your fuel pressure regulator is under the hood and is very much in play for delivering fuel pressure to the fuel rail. Pull the vacuum line off the fuel pressure regulator (and check condition of that line). Check for raw fuel in that vacuum line as well. It is possible as well that a faulty fuel pressure regulator could be the cause of the fuel pressure leakdown that you are experiencing as the vehicle sits.

Jumping the ballast resistor should not be a problem, it is done all the time. The fact that it runs for 10 minutes also rules out the ballast resistor.

 

^^^^^^^ Someone with more expertise.