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3 fuel pumps in 75 miles- HELP!!


 
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IndyMatt
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Joined: 09 Sep 2006

PostPosted: Sat Sep 09, 2006 5:41 pm    Post subject: 3 fuel pumps in 75 miles- HELP!! Reply with quote

1991 Cherokee Laredo 4x2 4.0

Typical fuel pump issue...I changed the pump and filter and went on my way. Not many miles and it started chugging again. I changed the filter. It was fine for just a couple of miles. Had it pressure checked...10psi. Obviously not good. I pulled the new pump and returned it. Got another new pump...installed it...ran perfect for about 45 miles then same thing. I replaced the pressure regulator but no change. I just went today and got another new pump. I'll replace the hose going from the tank to the filter tomorrow.

Basically, I'm losing pumps and not sure why. With a pressure guage on, I can see that when I turn the key on, no pressure builds at all. After long cranking, the engine will fire when 10psi is reached. When the key is shut off, the pressure immediately goes to 0.

Any ideas where I should look as to the cause of the pumps going out on me?

Thanks- Matt
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monkeyman3875
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Joined: 06 Jul 2005
Location: Charlotte, NC

PostPosted: Sat Sep 09, 2006 7:50 pm    Post subject: Reply with quote

First, what do you mean by chugging. Chugging as in: have to keep the pedal down to keep the car running. OR. Chugging as in: sounds as if one (or more) cylindars isn't firing. Someone correct me if i'm wrong but...

If it's the first, it's most likely a leak in either the hose or the pump or regulator. If it's the pump/regulator I would guess (and I'm no electrician) that there's a short somewhere and you're frying your pumps. If it's a leak, you should see it.

If it sounds like one cylindar's not firing, it's probably one of your injectors. It could either be the o-ring or injector itself. The o-ring would produce a noticable leak under the injector. The injector would leak into the cylindar causing you to smell gas out of the exhaust when you fire up the car.


Hope that helps.
John
_________________
-1997 Stock XJ
-4.0 L
-4-speed automatic
-130k Miles (and counting)-> let me know of any preventative maintenance you guys can think of. PM me.
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IndyMatt
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Joined: 09 Sep 2006

PostPosted: Sun Sep 10, 2006 4:05 am    Post subject: Reply with quote

Chugging as in its obvious there is a lack of fuel...back firing occurs.

I could feather the throttle and the get rpm's all the way to redline with a steady fuel pressure of 15psi. If I just put the accelerator to the floor, it would bog down and the rpms wouldn't go above 3k.

Definitely don't think it an injector. They wouldn't have anything to do with the fuel pressure correct?

I'm not seeing any leaks.

There is no unusual exhaust smell. In fact, redlining with 180k on the engine and still no smoke...that much I can say I'm happy with.

Now...going on the electrical route...I'll get the multimeter out today and make sure I'm getting a full 12 volts to the harness.

Thanks for the input. Truly appreciated!

Matt
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