1999 Jeep Wrangler 4.0 fuel pump problem


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1999 Jeep Wrangler 4.0 fuel pump problem

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fuzzy1
User

Mar 21, 2010, 7:25 AM

Post #1 of 3 (8277 views)

1999 Jeep Wrangler 4.0 fuel pump problem	Sign In

Hello again folks,
I have a friend with a 1999 Jeep Wrangler with a 4.0L. Guessing about 100,000 miles
This is the second time now they are having fuel pump problems.
The first time was the factory pump went bad. I replaced it with all new filters. In less than 8 months the new pump quit. I went with a different mfg pump 3 months ago, and now this is where it gets strange. Was driving and engine quit running. Pulled over and got some carb cleaner and shot into intake and engine runs. I depressed the valve in the port for checking fuel pressure and nothing but air pressure came out. I can hear the pump running for its 2/3 sec prime when the key is turned to on position and not getting any fuel out of the tank. There is a quick disconnect at the tank and no fuel there but again I can hear the pump running. I have also discovered what appears to me and excessive amount of vapor pressure in the fuel tank when removing the fuel cap. When I first loosened the cap pressure release was apparent but after about 3/5 seconds it continued so I clocked it. 17 seconds it took to release pressure from fuel tank before I could fully remove the cap, and stranger yet is the fact that the fuel filler neck has a valve built into it. It will swing out of the way when the gas station fuel filler hose pushes against it. Well after venting by loosening the cap I manually pushed the valve in and got a LOT more pressure to release from the tank and now even stranger yet, with the fuel cap off and just cranking the engine for 10 seconds will create a LOT of pressure build up in the tank. My friend said this pressure has always been like that since they bought the jeep new. So Im very concerned that this excessive pressure might be causing too much pressure on the pump and how or what do I need to check next. Im going to drop the tank again soon and check for a ruptured hose in the tank, again as I do hear the pump running.
Thanks,
Fuzzy1

nickwarner
Veteran / Moderator
nickwarner profile image

Mar 21, 2010, 9:50 AM

Post #2 of 3 (8273 views)

Re: 1999 Jeep Wrangler 4.0 fuel pump problem	Sign In

check for a pinched off or broken evap line. You're on the right track with this thing. This is way too much vapor pressure and is causing you problems

fuzzy1
User

Jun 6, 2010, 6:09 PM

Post #3 of 3 (8178 views)

Re: 1999 Jeep Wrangler 4.0 fuel pump problem	Sign In

Need to finish this one.
Turns out the fuel pump blew out of the tube inside the canister unit.
This has happened 2times now and im ready to get complete new unit from parts house.

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