dirty boy

1994 4.0 Cherokee Sport, stock...

I was driving down the highway this evening when my xj just died...I was doing about 120km/h (75mp/h) and the check engine light came on as the engine cut out...tried starting it and got nowhere...

After towing it home and poking around I found the burnt 30A fuse..I tried throwing another fuse in there and it popped when I attempted to start it...after the second fuse, it wont even turn over...

Im assuming that a dead short is most likely the culprit here, does anyone have any input? Any places I should start looking first? Ive been driving vws for years, this is my first venture back into a domestic and id like to have it up and running asap...

Thanks in advance!

dirty boy

No takers on this one? Ok. Can anyone tell me which years would have a compatible ecm? Ive done a bunch of visual inspecting of wires and everything looks intact...I think my next step will be to swap another ecm to determine if thats the culprit...

Turbo X_J

Hard to believe the PCM would pop a 30, it's got to be in the wiring or a connector somewhere. Disconnect the battery and start tracing the circuit from the fuse box, chances are the fix is free.

freegdr

What the label on fuse hole would be a good starting place...

dirty boy

Its the 30A maxi fuse under the hood, theres only one 30a engine control maxi fuse under the hood, and its not labelled with anything other eng ctrl 1...

Ive examined the wiring as thoroughly as I can without splitting the loom...the jeep is in great shape for the year, and only 115km on it...theres no chafe, no rub, no burn on any of the wiring outside of the loom, so its hard for me to consider inside the loom being in worse shape...the starter still cranks over, so I also have a hard time thinking its within the starting circuit...

So can anyone here tell me which other ecms are compatible with the 94s please?

freegdr

Does you pdc look similar to this if so unplug your fuel pum see if fuse still blows ...

dirty boy

Bingo! My maxi fuses are labelled differently, but the relays are essentially the same layout...and after pulling the fuel pump relay, the fuse doesnt pop on the turn of the key...

Again, the wiring all looks sound, and isnt hard or brittle anywhere I have access to, so im going to assume pump failure itself...off to napa I guess!

Thank you for your help!

freegdr

B4 that Id unplug the pump it self and replace the relay that will tell you if wiring to pumps not causing it.

dirty boy

I jumped the gun on that one for sure...

Fuse still pops after the new pump, so I tried spraying a little bit of gas into the intake to see if the engine would fire, theoretically implicating a faulty ecm...no fire, cough, or even sputter...so I unplug the ecm, replace the fuse, power the ignition, and the fuse remains in tact...I used a multimeter to make sure there was actually power going through the fuse, and it shows 12v...

Just on my way into the wreckers to grab an ecm to test the dead ecm theory...

freegdr

Guess you missed this step....

Turbo X_J

It's only money......

dirty boy

Totally missed it...and the new ecm didnt help at all...I really didnt want to start tearing into the harness itself, but its kinda looking like that will have to be my next step...

Without the ecm it doesnt pop fuses...how many pins out of the ecm could be relevant to this issue, and only popping this fuse?

dirty boy

Does anyone have an ecm pinout diagram?

freegdr

If you unplug the pump does it blow .....

dirty boy

Yes, it still blows with the pump unplugged...

if I pull the 60A ignition fuse it doesnt blow, and if I pull the fuel pump relay, it doesnt blow...but pretty much under any other circumstances, the 30A fuse blows...