Hello,
I've had my '92 Cherokee for about a year since buying it from my father. I noticed after my first off-roading trip in it that the fuel pump started whining when hot. This was in the middle of the summer last year and once the temps cooled off here in southern Nevada the issue went away. Fast forward to this summer and the problem came back. I decided to replace the pump since I didn't know how old it was or what brand it was (I know to avoid Airtex). I ordered a new Delphi pump assembly and this one is just as bad if not worse than the old one as far as noise. Even when it's been sitting overnight it will still hum on startup and progressively get worse as I drive it in the heat to the point that you have to turn up the radio to drown it out. Scouring this forum and talking to people irl I put together a list of causes that are likely to be my issue:

-bad fuel pump (seems unlikely since it is brand new)
-fuel pump assembly installed incorrectly (the pump went in very tight and was difficult to seal)
-clogged vent line
-clogged fuel filter (I didn't replace it when I did the fuel pump)
-fuel pump relay (not sure how to troubleshoot this one besides replacing it)
-no insulation(?) on top of tank to prevent the tank from touching the body of the vehicle

I noticed too that when we changed the pump the tank it self was very loose and we snugged it up after installation. It seems unlikely that the brand new pump is faulty and this issue only came about after that off-road trip last year (my dad never reported fuel pump noise issues in the 22 years he owned it) and I do not recall having this issue at all during the fall/winter/spring months.
Just looking for some insight into this issue and to see if I could be missing another cause. I will probably end up dropping the tank to inspect it this weekend while I am doing the fluids on the axles and transmission.

 

brand new means nothing nowadays, sorry but is the world we live in now

 

Yeah if I can't figure out what the issue is I'll just get the pump replaced under warranty and try another.

 

"I will probably end up dropping the tank to inspect it this weekend while I am doing the fluids on the axles and transmission."

that is the best idea....go through and recheck everything.....

nothing should have to be forced to go back together...

 

I inspected the old pump and the rubber piece on the return line (I think that's what it is called) is missing. So it is either floating around in the tank or it is stuck in the spot where the new one would sit. This might explain why I had so much trouble getting to in.

 

The Delphi pump in my 96 has whined for the almost 4 years I've owned my Jeep. The pump was new when I got the Jeep.

 

I would check that the pump is not touching the bottom of the tank because the tank will act like a speaker if it touches the bottom of the tank , it should be floating just off the bottom and the tank should have some insulation to stop the tank from touching the jeep to help keep pump noise for the jeep .