My 94 cherokee has decided to blow the Engine control 1 fuse and i get no spark without it. its supposed to be a 30 amp but the guy before me put a 50 amp in and it blew that too. i owned the jeep for about 5-6 months before it blew the fuse the first time and i replaced it. it blew the fuse again two days later while wheelin and now it will run for 5 seconds and blow it again. does anybody know what goes to this fuse so i can can find the wire thats grounding?

 

Fuse in pdc mini one.?

 

Might check over the sensor wiring, particularly the O2 sensor for abraded insulation or damage. That seems to be a common trouble spot.

 

its in the pdc but its a big fuse

 

i took apart the fuse box and followed the wires from that fuse and they go to the ECU. i found exposed wire but i fixed it and it still blows the fuse. could the ECU be bad? previous owner said he already replaced it once..

 

Fuse that big blowing is a dead 12 volt to ground short needd wire diag see what that fuse powers...

 

When did the fuse blow exactly? What where you doing exactly ever sunk your jeep in water?

 

ive never sunk it in water and it blew when i was climbing up a small hill. i rolled back down it and it blew another one when it was flat.

theres one wire that gets hot going to that fuse because theres melted tape on it. the wire starts at the ECU and splits into thre wires that go to the blown fuse, fuel pump relay, and engine control 2 fuse.

ill look through the wiring diagrams and try to find everything that goes to that fuse

 

sounds like a wire is rubbing on the chassie somewhere... and it grounding out...

 

i know. but i followed the wire that goes to that fuse and theres no damage to the insulation or anything but its definitely getting hot because it melted the electrical tape around it.

 

If the ECU power wire is running hot, either it or something connected to it is drawing too much current. Or the wiring is damaged.
I'd put an ammeter inline with the fuse to measure the current draw, (most DMM's have that function)
Then pull the plugs on the ECU and see if the current draw drops to zero. If it does not, there is a wiring issue. Shake the harness a bit to make sure nothing changes.
Inspect the ECU plugs and sockets to make sure there is nothing foreign, or bent pins, etc.
Next disconnect everything powered by the ECU one by one to see if the draw drops substantially. O2 sensors, TPS, IAC, etc.
Also check the wiring leaving the ECU and feeding each sensor or control to see if it is getting hot.
Last thing I'd try is swapping the ECU itself, if the current one is scrapyard, or a bad reman, it may have failed.

 

Have you climed underneath and looked at the wiring yet ? Un plug fuel pump see if it still blows ....

 

yes this is what i was thinking...

 

ok so i unplugged the fuel pump and tried starting it and it didnt blow the fuse but when i plugged in the fuel pump it still didnt blow the fuse and now i have no spark with a fuse in either.

 

No spark from fuse?