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Unread 05-27-2005, 07:07 PM   #1
1995yj1978cj
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Electric Fuel Pump Issue, NOT pump

Hi this is my first post, I have read almost all the posts on this site and hope someone can help me out.

I have a 1995 YJ with a 2.5 liter 5 speed.

I replaced the fuel pump last weekend because it was not pumping fuel when the engine had sat for about 15 min or more. If i turn the key on and let it sit for a while, or turn it on and off for a while and try to start it, I get a growling sound under the hood that last for about 10 to 30 seconds. As soon as the growling sound stops the fuel pump kicks in for about 3 seconds and the jeep will start right up and run fine until I shut it off and let it sit again for 15 minutes or so. I have started it and shut it off then immediatley turned the key back on and sure enough the fuel pump will come on for 3 seconds and the Jeep will start right up.

I was lucky enough to track down the clicking/growling sound to the auto shutdown relay and replaced it. Still doesn't work, and still makes the same noise for 10 to 30 seconds then the pump kicks in and you know the rest.

Anyone got any ideas? It seems to me that there is a circuit that works when the engine is running but doesn't when I try to start it. I know with some older GM vehicles the fuel pump has a backup circuit that works when the oil pressure is over 5 PSI, but while cranking the engine it pumps up to about halfway so if it had the same circuit it would pump.

HELP!!!

Thanks,

James

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Unread 05-27-2005, 09:58 PM   #2
sentinal02
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if the ASD relay was switching rapidly like that, the fuel pump relay was likely also doing it. they're controlled by the computer on the same circuit. try changing the fuel pump relay as well. there's been a number of posts in the past about the same kind of relay chatter as you described and it usually ends up being the ECU that's gone bad. the only other reason i could think of that would cause the computer to cycle the relays like that would be a loose/faulty ign switch that causes the computer to cycle on and off like that. I'd see if you can find someone local with a 95 2.5 like yours and swap computers to see if the new computer does the same thing.
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Unread 05-28-2005, 08:51 AM   #3
1995yj1978cj
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New info

I went out and checked the jeep again. When I turn the key on the engine light will not come on. BUT when the "relay chatter" stops the engine light and upshift light come on and the engine will start. Is there a relay that kicks in the ECU? The jeep will run forever if I don't shut it off and leave it off for more than a few minutes.

I also found out that if I shut the engine off and turn the key back to the run position and leave it that way for a long period of time it will work. I left it off for 30 minutes at one store and then once I got it started I went to another store. Once there I shut it off and turned it back to "run" left it that way for about 30 minutes. When I came out I started the jeep without issue. I did this twice more after that and it worked. Any ideas?

James
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Unread 05-28-2005, 10:48 AM   #4
sentinal02
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definitely sounding like the computer. everyone else with this problem said the same thing about the check engine light not coming on immediately. there's no relay that turns the computer on, just a control wire from the ign switch that signals the ECU to energize.

check out this thread for what pins do what
http://www.jeepforum.com/forum/showt...ghlight=CEL%2A

and here's one with what sounds like the same problem you're having:
http://www.jeepforum.com/forum/showt...ghlight=ECU%2A

HTH
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RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
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Unread 05-28-2005, 12:12 PM   #5
1995yj1978cj
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The second link is mine exactly

The second is exactly what mine is doing. I can not believe that it is the ECU since it will run forever once it is running and if I shut it off but leave the key on I have no problems. I will post to that thread too.

James
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