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Unread 04-06-2005, 08:51 PM   #1
jtag83
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Join Date: Apr 2005
Posts: 2
Intermittent Fuel Pump Problem

I have '93 Grand Cherokee with the 4.0L One day I noticed a little engine stutter right after it started. A few days later I shut it off and it wouldn't start at all. I waited 5 min and it started and ran fine. Two days later I didn't dare leave the driveway because it was stumbling and didn't want to run. Day after that it ran fine. Died the next day at the end of the driveway.

I took the fuel filter off and replaced with a new one. Started up and then died again. Wouldn't start so I checked for fuel at the rail. No fuel at all. Later it started fine, quit and then would restart, but wouldn't really run. There was fuel at the rail.

Tonight I started it and it ran for a few minutes before it quit. I tapped on the fuel tank with a rod and it restarted. While it was running I would listen for it to begin stumbling then I would tap the tank. The motor would smooth out, run for a while and stutter. Tap. Smooth. Stutter. Tap. Smooth. Stutter. No tap. Dead.

One time when it was running smoothly I hopped in and brought the Tac up to 2500 and held it there...for many minutes and it did not die. As soon as I let off the gas it quit.

Is this due to a bad fuel pump? If so why would it run at high RPM, but not at low? If I need to test voltage at the pump...where do I do it?

Thanks,

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Unread 04-06-2005, 09:20 PM   #2
todd17063
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Join Date: Mar 2005
Posts: 44
sounds like my problem.. and it has me baffled. one time it fires up, the next it won't start. one time you hear the pump prime the next nothing at all.i'm afraid to drive mine around the block for fear of having to push it home. if you figure it out email me at todd17063@aol.com thanx

Todd
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Unread 04-10-2005, 10:13 PM   #3
jtag83
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Join Date: Apr 2005
Posts: 2
Any mechanics read this discussion?

Tonight I started the jeep and ran it up to 2000 RPM. I let it run for 20 minutes. After I removed the stick to let it return to idle, it died within a minute or 2. That doesn't lead me to believe that the fuel pump is bad.

Any opinions?

Jerry
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Unread 04-11-2005, 05:43 AM   #4
greasefingers
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1994 ZJ 
 
Join Date: Sep 2003
Location: Northern VA, USA, NJ
Posts: 8,237
I would not trust a twelve year old Jeep fuel pump!

Most of the relays in the Power Distribution Center, located behind the battery, are the same; so you can play musical chairs/relays with them first to eliminate a relay. You also measure the fuel pressure at the fuel rail if you have a gage. Turn the key is listen for the relay and the pump whining.
You can also disconnect the harness at the gas tank. Measure the resistance across the pump and check to see if battery is getting to the pump.

My fuel pump quit the winter of 2004, in my 94 ZJ. I had to hacksaw the gas tank hanger bolts off, because NJ spreads a lot of salt on the roads. I paid $ 309 for the pump at a local parts store.
1- Test the hanger nuts for removal. If they need to be sawed off due to rust from winter salt, then buy two new bolts & nuts first at the Dealer before proceeding.
2- Hand-pump the gas out of the tank.
3- Jack the rear up a little for better access when dropping the tank
4- Disconnect the gas fill & vent line from under the rear driverís side fender.
5- Support bottom of gas tank with a jack
6- Remove gas tank hanger bolts. I used a hacksaw blade in my hand with a glove. There is no room to saw with the hacksaw blade in its frame/holder.
7- Disconnect electrical harness.
8- Remove the three gas lines going to the tank near the filter, because you do not want any gas vapors while sawing the hanger bolts. Drop tank, remove crappy pump & completely wipe in inwards out with several rags & use some gas to clean it even more. Spend as much time as it takes to clean the tank. Very important.
__________________
Cheers Steve

94 Black Laredo 4-Liter with QuadraTrac (42RE trans & NP249 TC) 200,000 + miles purchased new

88 Cherokee 2-door with 5speed manual 139K miles(deceased) purchased new
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Unread 09-06-2007, 09:43 PM   #5
blitzen15
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Join Date: Sep 2007
Location: Muskegon
Posts: 2
i have this same problem in my '97 ZJ. my dad has been a mechanic for 25 years and both of my older brothers do all their own mods and auto work. not a one of us knows what the problem is. i desperately want my jeep back because i'm afraid to drive my grand am in the winter
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