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Unread 08-16-2006, 04:54 PM   #1
rkreger2
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Fuel pressure and pump

I had a small slow start problem a week ago. I since changed the fuel filter and now I have a MAJOR slow/no start problem. With a gage I can not get pressure over 12psi when cranking. If I bleed a bit of fuel from the pressure port I can get it to start after a lot of cranking and bleeding. Once it is running I get about 20psi of pressure. This seems really low!! It drive OK, but seems pretty sluggish. Once I turn it off the pressure just falls off immediately.

It seems like a priming issue but while running I only have the 20psi which seems low. Is this the check valve going out in the pump? I am wondering since I changed filters if I didn't just kill it somehow. What do you guys think?? I don't want to pull the tank if I am chancing the wrong thing.

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Unread 08-16-2006, 04:59 PM   #2
rkreger2
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I forgot to mention it is a 2001 GC 4.0L with 107K on the dial. I just had to change the water pump and did the fuel filter at the same time .
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Unread 08-16-2006, 06:53 PM   #3
Test
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Sounds like a bad fuel regulator and/or pump.
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Unread 08-16-2006, 07:24 PM   #4
greasefingers
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I would change the filter again since it was better with the old one. Maybe the new has something lodged in it. Hint: buy it from a different place just in case that the whole lot of them is funky.

Your pressure should be almost double from what you are getting. If a new filter does not help then a new fuel pump would be next unless something is in the line or the fuel rail is rusted.
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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 08-17-2006, 11:33 AM   #5
rkreger2
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I think I am going to change the filter one more time. It is much easier than the pump and doesn't cost much just to be sure.

One question though, does the fuel filter on the 01 (remote mounted in axle housing) have a built in reguator inside the filter. It has 3 connections on it. 1 from the pump, one to the engine, and one back to the tank. I'm really questioning this since it got bad right when I changed the filter.
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Unread 08-17-2006, 11:36 AM   #6
greasefingers
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Canít help ya. ZJs only have 1 inlet & 1 outlet.
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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 08-17-2006, 10:12 PM   #7
Test
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Try this http://www.wjjeeps.com/fuel_filter.htm
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Unread 08-17-2006, 11:13 PM   #8
ktplotts
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Yes, the 01's have the regulator in the fuel filter. My book says that if your pressure doesn't reach normal range, 44.2-54.2 PSI, then check for restrictions, and then replace the pump. If it is higher then specified, then replace the regulator/filter.

I'm having a opposite problem, Its fine while driving, but after sitting, it looses all pressure.
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Unread 08-18-2006, 12:04 AM   #9
Redbob
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Quote:
Originally Posted by ktplotts
I'm having a opposite problem, Its fine while driving, but after sitting, it looses all pressure.
I wouldn't be too surprised if that was leaky injectors; do you get just a little smoke on startup, and it briefly runs a little ragged too?
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Unread 08-18-2006, 12:20 AM   #10
ktplotts
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no, not at all. Pretty sure i got it narrowed down to the fuel filter/reguator. I ordered it last week, it just takes a while to get here.
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