Sir Jeep-a-Lot

F6 fuse is still good I think.

That's what it looks like according to the FSM...fuse F15.

So if that fuse is blowing, it means there is too much current coming from somewhere, yeah? could a bad ground cause that? I need to check grounds asap. I read that issues with the O2 sensor(s?) on ZJs can cause the PCM fuse to keep blowing...could this possibly go for XJs as well?

that seems logical, though, the only thing I did when changing the pump was unplug the old pump wire harness and plug the new one in...

ET JEEP

Fuse 15 is what I show too. If that fuse is blowing something is shorting to ground somewhere. This fuse feeds pin 3 on the ECM, the automatic shutdown relay and the fuel pump relay.

Does the fuse blow just by inserting the fuse with key off? If so, the problem is the ECM, the wiring to the 2 relays or maybe the relays have a fault.

At $5 a pop it can get expensive. You might try removing the 2 relays and inserting a fuse. This will be just for the ECM and the wiring.

BTW, the wiring goes from fuse 15 to fuse 2 15amp then to the automatic shutdown relay. For the fuel pump relay it goes direct to pin 30.


The wiring at the fuel pump will only receive power when the key is turned on. The ECM turns on the 2 relays thus you hear the fuel pump run for a few seconds. The ECM then turns off the relays waiting for engine start. So a problem at the fuel pump will show only with the key on.

The O2 sensor is wired thru the ballast resistor bypass relay and would get power when the fuel pump relay is activated. Again the key must be on.

Sir Jeep-a-Lot

Yeah the fuse blows as soon as I put it in with the battery connected, and it also blows if I put it in first and then connect the battery negative. The ECM is the same thing as the PCM, yes?

Electrical isn't really my area of expertise...what exactly do you mean by this? What would cause something to short to ground...wires touching another metal part of the vehicle?

So after doing this if the fuse still blows, it would mean the problem is with the ECM or wiring, correct?

Found a thread here where someone was having the same problem of F15 fuse repeatedly blowing. Apparently, just cleaning the wires and connections worked? Hard to believe that alone would completely fix it.... http://www.naxja.org/forum/showthread.php?t=1079546

Gonna go investigate more...

Sir Jeep-a-Lot

Are relays like fuses in that once they go bad, they will just not work? or can they still function, just not correctly?

freegdr

did ya pull the relays then insert fuse ?

Sir Jeep-a-Lot

Just pulled the fuel pump & ASD relays, and the fuse did NOT blow. Does that mean the ECU/PCM checks out ok?

freegdr

ok what fuse keeps blowing work with me for a minute

Sir Jeep-a-Lot

There is also power at #30 on both those relays...though I'm not sure exatcly how much since all I have is a simple test light. I will go buy a multi meter if necessary.

What is the correct way to bypass the ballast resistor? I couldn't find a replacement locally, so I just snipped the connectors off and twisted em together for the time being...could this be causing the fuse to blow?

Sir Jeep-a-Lot

Its the larger 30A fuse second from the right in the F15 spot, labeled "Engine Control 1" and "PCM" in the manual

freegdr

did fuse start blowing after this...

freegdr

this one

Sir Jeep-a-Lot

Yup that's the one. You know, I didn't notice the blown fuse till a few days after it stalled, so it may have been AFTER I "bypassed" the ballast resistor...not totally sure though. Could it be that the ballast resistor first went bad, and THEN the fuse went out after connecting the wires?

freegdr

hello.....

freegdr

have you unpluged fuel pump and see if fuse still blew?

freegdr

dought it