Engine Control Fuse Blowing

somerowl · #1 (**permalink**) 08-10-2007, 12:34 AM

Hello, I've got a 1990 Cherokee Laredo 4.0L 250,000mi. with an electrical problem. The Engine Control Fuse blows within seconds of it being replaced and the engine starting. It originally had a "loss of charge" indication through the dash gage followed by the battery being drained as it limped home. I replaced the alternator, and then discovered the fuse blown when it wouldn't start. I replaced the fuse and it still wouldn't start. Discovered a bad distributor cap center (coil) contact and the coil wire completely corroded with nothing left at all inside the wire except for dust. I replaced the wire and distributor cap and the fuse, fired it right up and the beast blew the fuse again (about 5 minutes). Replaced the fuse again, found a bad ground wire at the block where there were about four other wires as well and fixed that. The fuse blew even faster, maybe 10 seconds. I've since discovered a stray volt with the negative cable disconnected, and have disconnected one at a time the indicator and sensor wires under the hood except for the O2 sensor and the computer. Nothing made the stray volt disappear.
PLEASE HELP! I'm trying to keep this fabulous beastie that tows my trailers and keeps my family safe in the snow with great four wheel drive, but I'm losing patience.. I'm a decent mechanic and am hoping for an "old timer" with some great advice to keep me from tracing this down one wire at a time.......
Thanks,

Saurian · #2 (**permalink**) 08-10-2007, 07:47 PM

Hmmm... The only thing I could suggest, and you might well have done this already, but check for burnt wires in the harness from the ECM to the firewall... My good buddy has a '95 Cherokee Sport, 4.0. He was heading home from work one day, and all of a sudden, the thing died. Just died. All kinds of lights and bells and whistles are going off, point is, it won't start... Ended up being a blown engine fuse, caused by the wire harness from the ECM melting and shorting on the exhaust manifold. I wasn't the person who repaired the problem, so I don't know more than that, but it's something to check out, I guess the wiring was totally melted together.

Sorry I can't be of more help. Welcome to the board. Hope you stay around and get to know people, we're a fun group