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  #1  
Old July 29th, 2020, 18:54
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xjerod xjerod is offline
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Fuel Pump Noise

I have a 91 XJ and i just installed a new Delphi fuel pump, now I am getting a humming/vibration noise from the pump. The odd thing is that if I disconnect the vacuum line to the Fuel Pressure Regulator (FPR) the noise stops. I am not sure if the issue is the fuel pump or the possibly the fuel filter. I also recently replaced the FPR but I put the old one back on and the fuel pump makes the same noise when the vacuum line is connected to either pump. The noise is constant while the Jeep is on. I am getting about 35PSI with the vacuum line connected and about 42 with it disconnected.

I have seen many people with similar issues but I do not want to buy another fuel pump and instal if it is going to do the same thing.

91 XJ
4.0
Automatic
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  #2  
Old July 30th, 2020, 04:48
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cruiser54 cruiser54 is offline
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Re: Fuel Pump Noise

Did you get that little rubber snubber installed on the assembly before going back together?
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  #3  
Old July 30th, 2020, 09:14
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xjerod xjerod is offline
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Re: Fuel Pump Noise

I did and I made sure it was seated properly, I dropped the fuel tank to ensure it was put back together solid. I bought a new fuel filter today and I will see if that has anything to do with it.
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  #4  
Old July 30th, 2020, 09:31
tempest411 tempest411 is offline
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Re: Fuel Pump Noise

Don't all electric fuel pumps hum? My '88 has always done that. I've owned it since '99 and have a couple different pumps in it.
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  #5  
Old July 30th, 2020, 12:11
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xjerod xjerod is offline
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Re: Fuel Pump Noise

I imagine the all hum to an extent but my old one did not and this new one is loud enough that I can hear it in the cab and even more so if I am behind the Jeep. I replaced the fuel filter and that is not it either...

Just weird that the vacuum line is effecting it because when I disconnect the vacuum line from the FPR the noise almost goes away. its like the pump is getting to much resistance and its causing it to make a noise.
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  #6  
Old July 30th, 2020, 14:06
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Re: Fuel Pump Noise

Make sure you have more than a gallon or two in the tank and then see if it changes.
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  #7  
Old July 30th, 2020, 15:26
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Re: Fuel Pump Noise

Filled it up and still does it... I hate to give up but I ordered another fuel pump.. I hope it goes better.
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  #8  
Old July 30th, 2020, 20:01
tempest411 tempest411 is offline
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Re: Fuel Pump Noise

Pulling the line to the FPR changes the pressure at the rail, which changes the load on the pump to develop that pressure. They say that when a pump starts getting louder it's an indication that it will fail soon. 'They say' is to indicate hearsay/rumor/urban myth possible...
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  #9  
Old July 30th, 2020, 21:26
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xjerod xjerod is offline
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Re: Fuel Pump Noise

At this point I hope it is that I got a bad fuel pump even though its brand new... these things happen but my luck it is another XJ mystery issue.. why do I have to love my XJ so much? if it were a grand cherokee I would of gotten rid of it.
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  #10  
Old July 31st, 2020, 20:37
my2monkeys my2monkeys is offline
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Re: Fuel Pump Noise

I would get an original Bosch from the junk yard and try it. Those aftermarket are junk. I still have the OEM pump in my 89 with 576,000 miles on it, but I do carry a Bosch spare under the seat.
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  #11  
Old July 31st, 2020, 21:09
tempest411 tempest411 is offline
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Re: Fuel Pump Noise

Quote:
Originally Posted by my2monkeys View Post
I would get an original Bosch from the junk yard and try it. Those aftermarket are junk. I still have the OEM pump in my 89 with 576,000 miles on it, but I do carry a Bosch spare under the seat.

If you read what people write in these forums long enough, every aftermarket fuel pump made is a pos. Trying to sort though it all can be daunting. The consensus I get is that Bosch and Delphi are pretty good, but everything else is junk. Airtex seems to have the worst reputation of any name brand available.
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  #12  
Old August 1st, 2020, 05:13
CJR CJR is offline
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Re: Fuel Pump Noise

Many, many years ago my 88XJ was "rear-ended" and the insurance company replace my fuel tank and fuel pump. That pump developed a "hum". I did a search for a "fix" and found one that required removing the fuel pump and trimming a metal bracket/plate to eliminate the hum. I decided to replace the fuel pump when it failed and not before. That was about 400,000 miles ago. That fuel pump still works just fine and the hum appears to have disappeared. The check valve, in the fuel pump, then failed and I corrected that by adding an inexpensive external check valve.

Best regards,

CJR
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  #13  
Old August 1st, 2020, 08:24
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xjerod xjerod is offline
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Re: Fuel Pump Noise

Did you trim the metal bracket that holds it to the gas tank? I guess that could be a vibration spot, I have a new fuel pump I was going to instal today but I will give that a try to see what happens. I also noticed that I am not hold fuel pressure at the rail so it could be that there is an issue with the valve on the pump and I was already considering the check valve.

Thanks
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  #14  
Old August 1st, 2020, 09:24
CJR CJR is offline
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Re: Fuel Pump Noise

To clarify. I never pulled the fuel pump. If you're considering an external check valve, get the all aluminium ones that are sold.

Best regards,

CJR
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  #15  
Old August 3rd, 2020, 09:42
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Re: Fuel Pump Noise

Soooo.
I'm somewhat of an expert on this topic.

here's my 2cents.... (7 fuel pumps in the last 15 years on my XJ)

Before I remove the fuel pump ballast. I never heard the pump.

After I removed it I can hear the high pitched whine.

Install a ballast if it really bothers you.
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