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Unread 08-14-2013, 07:42 PM   #1
Wiskey
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1991 XJ Cherokee 
 
Join Date: Oct 2009
Location: San Marcos CA
Posts: 487
91 XJ, is my fuel pump bad?

I went out wheeling, got out there a few miles, shut the Jeep off and then when I went to fire it back up it would just crank, but not start.

Every now and again it would kick, rev up then die again.

I tried the Off,On,Off,On trick to get the pump to prime and nothing.

Then I pushed in the little button on the pressure test port and no fuel came out,..

I was under the impression that a check valve should keep the system pressurized even when off, is that correct?


I had my friend turn the jeep on while I had the button pushed in and I got fuel spraying out.

But it still wouldn't start.

I ended up messing around with it for a while, got it to run for 20 seconds then die.

Finally I crawled under the jeep and tapped the fuel pump with something metal and it fired right up.

I haven't had a problem since, but whatever the problem was I want to fix it of course.

Does this sound like a fuel pump? Or should I be looking elsewhere?
Should it stay pressurized even with the pump off? Or is that a wrong assumption?

Thank you,
Whiskey

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Unread 08-15-2013, 05:01 AM   #2
XJaySC
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1975 CJ5 
 
Join Date: Feb 2009
Location: Charleston
Posts: 271
Usually, if something doesn't work until tapped on, I'll replace it for piece of mind. Though it does sound as that the fuel pump is the problem here.

Yes the check valve does hold pressure while running but the problem you described sounded like the pump not priming the system.
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Unread 08-15-2013, 02:35 PM   #3
mayeni
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1992 XJ Cherokee 
 
Join Date: Feb 2011
Location: kbh, Denmark
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I'm just curious, how did you tap the fuel pump, when it is inside the fuel tank? I assume you tapped the external fuel filter???
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Unread 08-15-2013, 08:11 PM   #4
Wiskey
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1991 XJ Cherokee 
 
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Quote:
Originally Posted by mayeni View Post
I'm just curious, how did you tap the fuel pump, when it is inside the fuel tank? I assume you tapped the external fuel filter???
You have a good point. I tapped where the fuel lines come out of the tank. I know that the fuel pump mounts to that bracket inside the tank so I figured it might help.

Whiskey
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Unread 08-15-2013, 08:24 PM   #5
Wiskey
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I'm going to go ahead and order another pump, I wish I could be sure it was bad, but based on where I am when it could break I think it is good insurance.

Thanks everyone!
Whiskey
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Unread 08-16-2013, 05:06 PM   #6
psychoteen101
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1996 XJ Cherokee 
 
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Could be a fluke, but ive seen a bad crank position sensor cause similar issues like this. When mine went bad, id be out wheeling, it would run fine until i shut it off, then would not restart until the engine cooled down. But if you hit on the tank and it restarted, its a good indication the pump is going bad. Hard to say if it runs fine now.
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Unread 08-16-2013, 05:21 PM   #7
Wiskey
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Quote:
Originally Posted by psychoteen101 View Post
Could be a fluke, but ive seen a bad crank position sensor cause similar issues like this. When mine went bad, id be out wheeling, it would run fine until i shut it off, then would not restart until the engine cooled down. But if you hit on the tank and it restarted, its a good indication the pump is going bad. Hard to say if it runs fine now.
Thats the thing that kills me!
Did your CPS test okay if you weren't having trouble? Or was the resistance out of spec?

Thanks,
Whiskey
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Unread 08-16-2013, 05:26 PM   #8
Wiskey
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1991 XJ Cherokee 
 
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Location: San Marcos CA
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BTW, who knew ordering a fuel pump would be so complex? I found a great kit that replaced the whole assembly, but when I researched the brand I couldn't find a single positive review reliability wise - everyone replaced them again 6 months later.

I ended up getting a Delphi which is supposed to be an OEM replacement and had great reviews.

I'd hate to have an issue again a few miles down the road. Of course then I had to order the screen and fuel filter separate, as well as the gasket. Hope I got the right ones.
Whiskey
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Unread 08-17-2013, 09:35 AM   #9
psychoteen101
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1996 XJ Cherokee 
 
Join Date: Feb 2010
Location: Gurnee
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My CPS was within spec when checking it cold. I think they just get heat soaked and intermittently fail. Only occurred while i was out wheeling. Jeep wouldnt run above 205, but it didnt seem to like restarting if i left it idling for a while. Once i replaced the CPS, it went away.

When my fuel pump went out, i bought a NAPA pump. Its been in there for a couple years. Ofcourse i only drive the jeep once a month since its strictly a trail rig, it seems to have been very relaible.
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