Ok I have a 90 F250 7.3 NA E4OD and i was driving it last night and she died. I have no power to anything, other than the lights. She wont crank, no radio, windows, heater, turn signals(except for hazzard) etc. Initially I thought it was the ignition switch so I changed it, but that wasnt it. It will crank if I jump the solenoid but I have nothing when I turn the key forward. I iginition rod and actuator work. So is there a main fuse or relay that may have blown??? I dont think it would be the pcm since from my understanding it pretty much controls the tranny. Anyone have this problem before? I only see 2 relays on the diverside fenderwell but they arent labeled...any thoughts??

 

I had a simlar problem on my 90 a few years ago, it started fine, started to leave the house, and it died like I turned the key. It turned out the fuel heater crapped out, burning out the fuseable link. Check the wires in the engine wireing harness that lays on the passenger side inner fender. Mine had 2 red wires mated to the fuseable link, then to the harness plug.

 

1990 and TWO relays on the Fender ???

One is for the starter, the other ????
The Glow plug relay should be on the back of the motor!

See where the wires go, the one for the starter should have a medium sized black (10Ga I believe) wire that runs from one large relay terminal to the starter, that would be the starter relay.

The starter relay, one of the large terminals is directly connected to the battery, there should be some small wires on that same terminal, one of them supplies the cab power I believe.

Like farmert stated, there are several fusible links in the harness in that area.

-Enjoy
fh : )_~

 

Well I figured it out. The cab power supply wire melted and burned itself in half inbetween the fusible link and battery. The fusible link is still good but the small gauge wire before the link is toast so I cut out the wire and fusible link and replaced it with one of those off the self fuseholder. I put a 30a fuse in it and got 500 yards and it blew out. So now Im left with trying to figure out what amp the fusible link was. The old link said 18gauge but gave no amp rating..Im assuming the cab does draw more than 30 amps but I dont want to put in too big of a fuse and burn the truck down..