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Fuel Pump not getting enough power??

H

Hammerite_05

NAXJA Forum User
Location
N.C.
I was not getting pressure in my fuel lines....my pump sounds like it is not getting enough power to pump. i have disconected the line where the filter is and it cant hardly even pump it through the open line. i bought a new pump and still the same problem....so i thought the pump i bought may have been bad so i swapped it for another and still the same problem!! i have 1 week and 2 days to get this thing fixed before a wheeling trip that I have planned on for a month.

does anybody know where the fuel pump relay is?? thats the only other thing i can think of to try.

please help
mac
 
Hammerite_05 said:
I was not getting pressure in my fuel lines....my pump sounds like it is not getting enough power to pump. i have disconected the line where the filter is and it cant hardly even pump it through the open line. i bought a new pump and still the same problem....so i thought the pump i bought may have been bad so i swapped it for another and still the same problem!! i have 1 week and 2 days to get this thing fixed before a wheeling trip that I have planned on for a month.

does anybody know where the fuel pump relay is?? thats the only other thing i can think of to try.

please help
mac
Click to expand...
1. What year? certain years have this pesky balast resistor in the engine that sometimes causes problems (resistor goes bad or the connectors to the resistor go bad).
2. How many volts do you have going into the pump?
 
i have heard about a Ballast register?? could that have something to do with my problem?? would i have one on my 1988 MJ?? ifso does anyone have a diagram of where it is??

mac
 
ballast resistor is on the drivers side fender. One wire comes from the relay, one wire goes to the pump. You can jump the ballast resistor with a proper guage wire to bypass it.
You should also check the fusible link attached to the starter relay. It's green and red I believe.
You'll need to get a multimeter if you want to troubleshoot the circuit.
 
ok,

here is are some pics to help us figure this BS out......



2 pics of the extra ground wire to test and see if that was the problem

ok,

DSC00136.jpg


DSC00135.jpg


here is the tank and crap

DSC00133.jpg



now to the other Question about the ballast

is the white ceramic piece in this pic it??

DSC00132.jpg


if so then i did the bypass and nothing better happened

DSC00131.jpg



this is about to drive me crazy!! i have got to get this done or i dont get to go on the wheeling trip March 4th


thanx

mac
 
that is the ballast resistor. Did you check the fusible link? Also, there's another plug for the fuel pump behind the drivers seat, under the carpet against the back wall of the cab. If you pulled on the wires to get the tank up there I could see you pulling it apart.
 
i checked the plug behid the seat and it was fine.......the pump is getting power but it seems like its just barely getting enough to hardly make a noise for about 1 sec.

i dont fully undersand where and what the fuesable link is

thanx for the help
mac
 
Could you just run straight 12V to the pump? If it runs, its a wiring problem, if not its in your lines?
 
Hammerite_05 said:
i checked the plug behid the seat and it was fine.......the pump is getting power but it seems like its just barely getting enough to hardly make a noise for about 1 sec.

i dont fully undersand where and what the fuesable link is

thanx for the help
mac
Click to expand...
It is on a timer, it will only run for 1-3 seconds when the key is turnd on.
Oh and don't run the pump dry it uses fuel for lube and cooling.
 
Last edited:
before all this mess the fuel pump used to run about 3 seconds now all i can get is about 1/2~1 second and no build up of pressure....with nothing wrong with the lines
 
Pull the fuel pump relay and jumper in place of it, or use another relay, I think all are identical, dont jumper the coil contacts. This should give you power to the pump, dont let it run too long. Just long enough to see if you get pressure. Is this a new pump by the way? I bought a new one and the polarity of the contacts were reversed from the original. So i had to reverse the wires as it was pumping backwards. Also after a week one of the hoses blew off so I had to reinstall and reclamp. Good luck.
 
Hammerite_05 said:
before all this mess the fuel pump used to run about 3 seconds now all i can get is about 1/2~1 second and no build up of pressure....with nothing wrong with the lines
Click to expand...
Just looking at your pictures again, I see a ground on the tank, the pump also has a ground is that good and clean.
 
jcnoble said:
Is this a new pump by the way? I bought a new one and the polarity of the contacts were reversed from the original. So i had to reverse the wires as it was pumping backwards.
Click to expand...

Ditto. Good catch. An easy one to mis one after market fuel pumps.
BSD
 
well, i went downstairs today (sunday) and just turned the key over and the pump came on so that the jeep cranked.....i was like how in the heck?? but i shut it down and tried it again.....cranked. then i tried to crank it a 3rd time and it went back to that stupid way that it was not getting enough power....so now i know the pump works....but i have a mechanic making a house call for me either tomarrow or tuesday and he is going to help me locate the short.

thanx for all the help

mac
 
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