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my truck lost all power on the freeway about a month ago and wouldn't start so i checked the fuel filter and the hose running from the engine to the filter not clogged. i got it towed into town and came back a week later started it up and drove it around for about fifteen minutes, seemed fine, went down the road a little bit and the truck lost all power again. i am assuming it's a fuel problem because there isn't any fuel coming out of the hose from the pump when the key is turned on. haven't had time to see if the pump is out or if it is an electrical problem. i finally got around to getting my truck to my place to look at it but still haven't had time because of work.

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An easy to to check your fuel pump is to pull the plug and run gator clips to the plug and connect it or touch it to a battery and if it pumps out gas you pump is good, most of the time anyways, so then from there if good check sensors and the bypass thingy on the drivers fender wall for the adjustment of power to the pump(Brain fart can't think of name), the check at fuel rail for pressure.

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I would check the condition of the ground located right behind the drivers side tail light. And I'd check the condition of the connector in that wire harness (it'll be right behind the drivers rear tire).

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and the bypass thingy on the drivers fender wall for the adjustment of power to the pump (Brain fart can't think of name).
That is the ballast resistor... ;) You can bypass it and see if it makes any difference.

 

Yeah! Thanks man, just couldn't think of the name for nothing :laughin:

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My '88 has been doing the same thing, and somebody else also reported this happening. In my case, I checked the ballast resistor and that was NOT the problem. Still baffled. Problem is, it's hard to test because I can't predict when/where it will happen. AAA only gives me four tows a year, and I don't want to use them all on the heap and have to go for eight months with no safety net for my wife, so I have been limiting use of the MJ to short trips that I'm fairly certain won't cause a stoppage. That avoids tows, but doesn't provide opportunities for trouble-shooting.

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weak F/P relay, or loose wire maybe?

 

Jeff

In my case, no. I have shifted relays around and it makes no difference. And it isn't a loose wire. It is time/temperature related. I drive for maybe 15 minutes, and suddenly the power dies off and it stops. And WILL NOT restart.

 

Sit by the side of the road for 30 to 45 minutes, and it starts up like there was never anything wrong. Something is getting heat soaked, but I can't figure out what unless/until I can get it to die while sitting in my yard, where I can unleash the testing crew on it without risk of getting clipped by a passing 18-wheeler.

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definately sounds like something is heat soaking, I agree (that's why I thought of a weak relay). Did you swap ICM's to see if that helped?

 

Jerry (tjbliley) was having the same random problem with his 2.5 rig awhile back....we ended up troubleshooting it to find out that one of the wires going to the TB injector was loose and intermittently loosing contact. That was a fun one to figure out.

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I've recently experienced similar issues with my '91 mj (2.5L) It started with it acting like it was running out of gas then smooth out (which it would do for about 2 minutes randomly) about 5 minutes after i got on the highway on my way to work in the morning, then about 2 weeks ago it would only start and run for about 5 seconds and crap out like it runs out of gas. I've replaced the fuel pump, fuel filter, fuel pressure regulator and map sensor, still nothing... I'm thinking its the ignition module too.. Anyone know where it would be located on my truck? I can't seem to find where it is.

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When I was active in the turbo Dodge community, what you describe as runs then just dies and won't restart, wait for 30 minutes or so and it starts right up, is completely indicative of a fuel pump in its last days.

That has been suggested, and that is NOT what I wanted to hear. But -- it may well be the problem. :roll:

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When I was active in the turbo Dodge community, what you describe as runs then just dies and won't restart, wait for 30 minutes or so and it starts right up, is completely indicative of a fuel pump in its last days.

That has been suggested, and that is NOT what I wanted to hear. But -- it may well be the problem. :roll:

 

I know it was suggested. Funny thing, I was all set to swap in a fuel pump off my parts truck. But I didn't want to listen to my friend that the CPS might be my issue. Going back and re-reading the Renix EFI manual, it might indeed be the problem. Ordered one though Rock Auto, should be here Monday.

 

Now I just have to worry about my friend doing his "I told you so" dance in my yard...

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my buddies car had the same problem and as the wires corrode at the fuel pump they get thinner, cause the wire to over heat due to the amount of amperage and voltage running through which then causes the pump to stop working, and then work in a little while. so we went to advanced auuto parts and bought 10 feet of 16 guage wire and re wired the whole dang thing. no problems since jamminz.gif

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I know it was suggested. Funny thing, I was all set to swap in a fuel pump off my parts truck. But I didn't want to listen to my friend that the CPS might be my issue. Going back and re-reading the Renix EFI manual, it might indeed be the problem. Ordered one though Rock Auto, should be here Monday.

 

Now I just have to worry about my friend doing his "I told you so" dance in my yard...

In my case, the CPS is brand new. Less than a year old and probably doesn't have 2,500 miles on it. It is always possible that it's defective, but it's a Jeep factory CPS and they very rarely spit out a bad one.

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  • 2 weeks later...

i was finally able to do a test today and the fuel pump does work. i also ran a test with the wires running back to the pump clip. you have orange, tan, and black. only the tan has a current, of course black doesn't because it is ground. i bought a volt tester so that's how i know. so where do i go from here? i don't have the internet at my place and when i can pick it up, it doesn't stay connected for long.

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Last week this happened to my MJ.

I experienced no power when entering the expressway trying to merge with traffic. But mine didnt quit, just didnt have any power. It acted like I was about to run out of gas. I limped allong to the next exit and got off. Upon slowing, I noticed a loud buzzing coming from the gas tank. Looks like my new pump crapped out.

 

Ran down and picked up a new on and threw it in, problem solved, buzzing gone and power is back. Who knows what happened, stuff breaks and aft mkt parts just are not as good a factory stuff...

 

Glad you fixed yours!!

 

CW

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i ran a wire with a fuse from the battery into the cab, hooked up a switch and spliced into the orange wire going to the pump, works just fine now, starts up every time, only died once but that was after fifteen minutes of it running, a friend said there was water in the fuel. i have driven about five hundred miles since fixing it without problems now minus that fact that when i push the gas pedal down to floor trying to accelerate fast it starts spuddering and seems like it is loosing power. so now i don't know what that is. also that little white piece that is in the engine bay that is bolted onto the drivers side near the front started smoking after i started up my truck for the first time in however long it was sitting, so i just unplugged the wires that went to it. so that might have been the reason i wasn't getting power to the pump, because when my truck first died there was some smoke coming out of the hood.

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i ran a wire with a fuse from the battery into the cab, hooked up a switch and spliced into the orange wire going to the pump, works just fine now, starts up every time, only died once but that was after fifteen minutes of it running, a friend said there was water in the fuel. i have driven about five hundred miles since fixing it without problems now minus that fact that when i push the gas pedal down to floor trying to accelerate fast it starts spuddering and seems like it is loosing power. so now i don't know what that is. also that little white piece that is in the engine bay that is bolted onto the drivers side near the front started smoking after i started up my truck for the first time in however long it was sitting, so i just unplugged the wires that went to it. so that might have been the reason i wasn't getting power to the pump, because when my truck first died there was some smoke coming out of the hood.

 

 

HOUSTON WE HAVE A PROBLEM

gibbs, you crack me up

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That white thing is the ballast resistor for the fuel pump. If you unplugged the wires that is probally your problem. I believe you can jumper the two wires together and run like that. The fuel pump will just be louder and may burn out faster.

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  • 1 month later...

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