Bad fuel pump/filter?

Hey everyone. I have been having some acceleration issues with my 2000 4.0 XJ. It will stumble, sputter, hesitate, until I get to WOT and then it jumps forward. It is especially bad at highway speeds around 70-80 mph. I have to be at WOT to maintain speed or it will sputter/stumble and lose speed.

I took it to Advance Auto to get the check engine code read and it gave a code for both O2 sensors. I knew the rear O2 sensor would show up as it has had a broken wire for a while, but the Jeep ran fine. I replaced the front and fixed the broken wire on the rear. The issue got worse after this (with the codes still being thrown, the guy at Advance Auto said the computer wont reset them for 500 miles ) and tested the fuel pressure. With the key on and the system primed, it was at 28 PSI. At a warm idle, 32 PSI. After I shut it off, over a few minutes it rose to 42 PSI, then several more minutes it fell to 38 PSI.

Should I go ahead and drop the tank to replace the fuel pump/filter or look more into the O2 sensor codes? Is there anything else I should check before dropping the tank?

Thanks for your time. I hope this all makes sense, I work 3rd shift and just got home.

Your fuel pressure is supposed to be 49.2 +/- 5 psi.

If you are going to go as far as to remove the fuel pump module to replace the pump inlet filter, pump motor filter, and the fuel pump regulator/filter, you might as well replace the entire fuel pump module.

Recommend a Bosch or Carter, not an Airtex.

You may have a damaged PCM from the damaged O2 sensor wire (from a short when it was damaged). The wire may still be damage down stream in the wire harness. Have you checked the O2 fuse and relay (If there is a relay?).

I would check the voltage at the fuel pump before I wrote it off or went in to replace anything on the fuel pump assy.

I had a similar issue a few years ago but mine was at 40-50mph. In my case it was either a dying CPS or TPS, I can't recall which.

As usual, the guy at the parts store is wrong. Re-boot the computer yourself, or simply clear the codes.

You should test your way to the root cause of the symptoms. Since you have had O2 issues, start there. Test the O2 sensors, inspect their wires, fuses and plugs. Test your Throttle Position Sensor (TPS). Test your Coolant Temperature Sensor (CTS).

Recheck the fuel pressure and as suggested check the voltage at the pump.

Once you have done some testing, you will be able to include or exclude some the usual suspects for the symptoms you have, and can proceed with either your diagnostics, or repairs.

Hopefully in the next couple days I'll get a chance to do some more testing. Perfect way to spend the holiday! Thanks and hope you all have a good thanksgiving

Since your fuel pressure reading is reading low you are most likely also are having to do the poor mans prime to get it to start. You will most likely be replacing the fuel pump assembly. I just did this yesterday. Not fun.
Purchased mine, Carter made in U.S.A., via rockauto.com.
You must drop the tank. The biggest hints I can give on this is are (1) the clip holding the fuel line onto the top of the pump assembly is a simply squeeze'n release. Just use needle nose pliers. It does NOT take any type of special tool. (2) The only two things to disconnect are the wiring connector and the vent. Once out of the Jeep the fun will be cleaning all the dirt from around the LARGE threaded ring holding the pump assembly in the tank. (3) Also make sure you get the tank as empty as possible. Even 1/4 or 1/8 of a tank of gas is not fun to deal with.

GAPanda, which Carter did you order? $93 or $178?

Also, can you siphon out the gas after dropping the tank?
Does the make things easier?

Would having a 2nd person on hand make this job easier?


CARTER Part # P74186 In Tank Pump & Strainer Set
Features CleanScreen Technology
$93.79 $0.00 $93.79

CARTER Part # P75040M
Features Turbine Technology
$178.79 $0.00 $178.79

Well, the TSP tested good, but while testing that I noticed that the Idle Air Control Module kept clicking when the key was on, and when the throttle body was turned it gave a loud click.

GAPanda, I would also like to know which Carter part # you ordered.

Thanks!

Soundslike the IAC is broken, but you need to isolate the click for sure.

Anyone have a write-up of how to test the TPS?
I'd like to see the "sweep" or whatever it supposed to happen.