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Old June 7th, 2009, 06:57 PM   #1
njracer23
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Exclamation Wont stay running.....Help!

Ok so i sold my buddy my XJ about 2months ago.

About 2 weeks ago he was on his way to go wash it after playing in the mud a couple hours away and she just died (keep in mind he drove it home a couple hours, it sat overnight, and he drove it again before it died). We checked the fuel pressure and it diminishes after about 2mins of idleing. We replaced the fuel filter, fuel pump, and swapped the pressure regulator. Still not holding pressure. The lines are all fine and its not leaking anywhere. You can hear the pump building pressure before its started. It doesnt appear that it keeps running or something.....what can it be? The only other thing i can think of is the computer is shot or something.

Any help would be appreciated.

Nic
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Old June 7th, 2009, 07:04 PM   #2
gregy133
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you could have injectors that are stuck open leaking fuel
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Old June 7th, 2009, 07:08 PM   #3
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But wouldnt it still stay running? When i let it build up pressure and i watch the pressure it just barely starts to diminish like a couple pounds in 5mins
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Old June 7th, 2009, 07:11 PM   #4
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ya it would be odd but that seems like the only other place if every thing else is good
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Old June 7th, 2009, 07:18 PM   #5
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Quote:
Originally Posted by njracer23 View Post
But wouldnt it still stay running? When i let it build up pressure and i watch the pressure it just barely starts to diminish like a couple pounds in 5mins
you say it starts to drop off after 5 mins.... is that with it running or with it off and the key on?
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Old June 7th, 2009, 07:23 PM   #6
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Quote:
Originally Posted by wrifrocks2005 View Post
you say it starts to drop off after 5 mins.... is that with it running or with it off and the key on?
Actually it drops slowly the entire time...but was about 2lbs every 5mins that was with it off.
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Old June 7th, 2009, 07:30 PM   #7
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If the ignition is off, then the fuel pressure will drop. What does the pressure do when it is running and stalls out?
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Old June 7th, 2009, 07:35 PM   #8
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It just diminishes to zero and stalls out. Like the pump wasnt even on....thats why i was thinking something with the computer. It turns on and primes at the beginning but after that it seems to not run
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Old June 7th, 2009, 07:47 PM   #9
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Cycle the key a few times, engin not running. What is the pressure? key off monitor pressure for 5min, *** You never said what year assuming it's a 96 and newer fuel pressure should be 55psi (+/- 5psi)***
Fuel pressure should not drop below 35 psi in 5 min, if it does the next step is to start over build your pressure back up, (engin not running) then pinch off the rubber fuel line after the fuel filter (engin side) and monitor fuel pressure again. This will test the injectors. Monitor fuel pressure for 5 min.

If you are holding fuel pressure with either test above this would lead to checking power to the pump. Check voltage at the ASD relay with a 12v test light, when the key is cycled it should illuminate bright but only for 4-8 seconds. You may need a wiring diagram to full test circuits between the PCM and the fuel pump, if all you circuit have good contiuity it is also a good idea to load test them to see if they will carry current.

Last edited by JEFF; June 7th, 2009 at 07:56 PM.
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Old June 7th, 2009, 07:59 PM   #10
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he was mudding I would recheck the connection at the fuel pump
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Old June 7th, 2009, 08:01 PM   #11
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It is a 93 HO. When you cycle the key the pressure is about 34psi.
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Old June 7th, 2009, 08:16 PM   #12
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Quote:
Originally Posted by njracer23 View Post
It is a 93 HO. When you cycle the key the pressure is about 34psi.
I would still try to monitor fuel pressure and see how far it drops. It shouldn't drop more than a few psi, 10-12 at the most.
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Old June 7th, 2009, 08:24 PM   #13
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How long does it run before the fuel pressure drops, and how quickly does it drop?

I know the pump is new, but it might be bad. You also might have a pinched line or like said earlier a bad connection to the pump.
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Old June 7th, 2009, 09:23 PM   #14
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Pull the vacuum line off the pressure regulator see if stays running.
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Old June 9th, 2009, 02:57 AM   #15
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I had my fuel pump start acting weird when a wire started corroding though under the carpet.
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Old June 9th, 2009, 06:04 AM   #16
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Does it keep fuel pressure when cranking?

And when running?
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