cwterry

Hello all. I am new to this forum but it seems to be a good community. I have a 1991 Jeep XJ 4.0L 4X4. I have owned it since 2007. In all, I have gone through 6 fuel pumps, three of which have been replaced since December 2009. I have no idea what to do. The pumps start to whine and grind and in some cases I break down completely so I park it and go get a new pump only to have it happen again. The tank is clean, the filter is replaced everytime and the strainer on the pump is new. The last pump I had only lasted 1 month!! My current pump is a universal inline installed between the tank and filter and it is rated at 95psi. Ran fine for two days now under hard passing acceleration it surges. I have the 12volt harness hooked to it but get 10.3-10.6v according to the voltmeter at idle. Upon revving the engine hard it will go to 11.5-12.0v on the meter. I think this is normal but please inform me if it is a factor. Thanks a million guys.

Cody

4jeepers

I think that you should be putting out about 13 to 13.5 volts from your alternator so I would check that out! Also check to see if you have a ballast resistor in line with your pump if so replace it as they are cheap and a bad or no resistor will burn out a fuel pump. I don't know if your 91 has one. I do on my '88. Good Luck

swells

I replaced mine 3 times until I got one that works. the fuel presure should be about 28psi I don't think the voltage would matter unless it was real low.

X-J

I had this issue and it went away after 2 pumps. (88 XJ)
I figured that the voltage running from the battery to the rear from a little wire that it would be a lower voltage.
When the pump did not work i ran jumper cables with a jumper wire to the positive wire on the pump and the pump turned on, and started the heap, then tuned the engine off, reconnected the connectors and the pump worked as it should.
I never found out why, and Im not being of much help, i know there is a relay for the pump but where is the 'ballast resistor' located ?

edit: also the repair manual tells you what the voltage is supposed to be to the pump.

cwterry

Thanks alot gentlemen. I will research these items and post back later with the results. Thanks again guys.

Cody

4jeepers

The ballast resistor is the white ceramic rectangle on the driver side of the engine bay. It has two wires connected to it and is held on with one screw. I know that you have one on your '88. They can start to fail and are cheap to replace!

X-J

I remember, thanks
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danimal

When you replaced the pump the other times, did you check inside the tank to make sure there wasn't any crap. The last one I did, I had to pull the fuel tank and there was a bunch of stuff in it. Rust, dust, silicone bits, pieces of hose etc.

Previous owner must have owned stock in 3M silicone and sealer division. He sillyconed everything.

The little sock/filter that fits on the pickup will block some, but not all stuff. The biggest cause of pumps failing is crap getting run through em. If you don't clean out the tank it'll just keep happening.

Either that or you've been extremely unlucky with new fuel pump failures.

Link with pictures of what I found in mine.

https://www.cherokeeforum.com/f2/fun-fun-28472/

cwterry

Thanks Danimal--I have cleaned the tank several times. Enough to know where the baffles are located inside that I dream about it at night!! Who knows with all the garbage gasoline we are sold nowadays? I used a vinegar solution and then some alcohol to dry it out. It seemed to be clean enough to eat from. Thanks again man.

Cody

danimal

Sorry I should have read your original post more carefully. I see now where you said you cleaned it.

Beats me then.

Must just be a bunch of bad pumps. Don't know what else would cause em to take a dump like that.