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update: 0 psi fuel pressure when running?

C

cjben

NAXJA Forum User
Location
Illinois
ok,thanks to those that were trying to help me with my jeep not staying running(thread title:would codes 12 and 24 cause these sympthoms?) Today is the 1st day in a couple days I have had a chance to work on it. Thought I would look closer at the fuel pressure. I noticed the pressure jumps up to 40 when I turn the key on. When the engine starts,the fuel pressure drops to 0 and the engine dies after about 3 seconds.then the pump cycles again and the pressure jumps back up to 40. I did replace the fuel pump,but I had driven about 40 miles on the new pump before this problem started. I really want to make sure this is fuel pump related before I take it all out again. any other reason the pressure would drop like this other than the fuel pump? and what would be wrong with the fuel pump to cause this? thanks again for the help....Ben
 
cjben said:
ok,thanks to those that were trying to help me with my jeep not staying running(thread title:would codes 12 and 24 cause these sympthoms?) Today is the 1st day in a couple days I have had a chance to work on it. Thought I would look closer at the fuel pressure. I noticed the pressure jumps up to 40 when I turn the key on. When the engine starts,the fuel pressure drops to 0 and the engine dies after about 3 seconds.then the pump cycles again and the pressure jumps back up to 40. I did replace the fuel pump,but I had driven about 40 miles on the new pump before this problem started. I really want to make sure this is fuel pump related before I take it all out again. any other reason the pressure would drop like this other than the fuel pump? and what would be wrong with the fuel pump to cause this? thanks again for the help....Ben
Click to expand...

Ben I am betting it is fuel pump and Im betting you bought an aftermarket not mopar part right?

also did you replace the fuel filter on the Drivers side frame when you replaced the fuel pump?
 
Did you try swapping fuel pump relay and make sure it is not loose. The ASD should be checked also.
Good luck!
 
The relays should be in a power dist center under the hood, sorry its been awhile since I looked at my son's 91. I am a little more familiar with a 96 which has OBD-II electrics. Your 91 may not have ASD. Someone else needs to jump in here.
 
on mine (1991,5spd)its not the auto shutdown relay or the fuel pump relay since i had them both jumped,,,,,,on that note, when I jump the fuel pump relay the pump stays on, what tells the pump when to turn on and off? I know fuel pressure should, but there isnt a sensor/switch anywhere on the line that I can see.
 
thanks for the help guys. I bypassed the ballast resistor,and it started up and ran great. do I really need this part,or can I just leave it bypassed? what would cause it to fail so suddenly? thanks,Ben
 
Ya, I have an update, I just looked at my jeep and the ballast resistor is broken in half and corroded......hmmmm seems like the problem.

Since I bent my fuel rail banging it to get the crud out I just need a new fuel rail.....but thats the problem, ballast resistor




BALLAST RESISTOR!!!!!!!!!!!!!!!!!!!!!!!
Driverside firewall/fenderwallish area, big white ceramic crap....
 
thanks creeperjeep,for your help.....i did figure out about 15 minutes before you posted about it from searching on here myself that it was the resistor:)
 
cjben said:
xjnation...yes,it was an aftermarket pump,and yes I also put in a new fuel filter when I changed the pump
Click to expand...

The reason I mentioned it is because Ive never had one last over a month that was not factory unit. The factory walbro units are top notched the bosch just dont cut it.
 
xjnation,the sticker under the hood says it's a 92,the title says it's a 92,and it has the 4.0 HO,so I am guessing it's a 92. I am not sure when they stopped putting ballast resistors in them,but that is for sure what it is,from what you said and searches I have done. thanks for your and every one else's help!!!:)
 
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