Complete electrical failure

[Poorman]

I have a f350, 1986,crewcab,manual trans, 6.9. Just drove 450 miles to my hunting camp, parked for four days, went to leave and everything was dead, like a dead battery, but the batteries were good, messed with it for an hour and then suddenly power came back on. I fired it up and got about ten feet and it shut down again. Crawled around for a few hours looking for something obvious, nothing so I made a jumper wire from a cord I had and jumped to the fuel shut off valve and then one to the glow plugs and then to the starter selonoid and it fired right up. I drove back home like that, I kept watching for power to come back on but it never did untill the morning after I got home, opened the door and the dome light was on so I turned the key and full power. I'm leaving next week again and I really need to figure this out, otherwise I'll be a little stressed knowing it could shut down again at anytime. Most every thing I've read points toward grounding, so I cleaned the two grounds from the batterys to the block, I thought it was interesting that with those two grounds off it would still turn over although pretty weak. So I'm thinking the ignition switch but the dome light and head lights seem to work independent of that switch (they come on when the key is removed) and when it shuts down they also go off. Any ideas?? electrical is always a bit confusing with me

 

[Noiseydiesel]

I venture to say. . . you have a bad fusible link off the solenoid.
Locate the solenoid and look at the outside of the wires. Chances are you won't notice anything.
Take each one individually and pull. The good ones won't stretch. The bad one will stretch because the wire melted inside the insulation.
Now comes the fun part.
Get yourself another link of the same gauge.
Buy two or five.
Install and see what happens.
Did the old one fail with age?
Usually doesn't but an outside chance it might have.
Hook it up and feel the wire. is it warm? You have a short.
somewhere.
Not warm? Turn on the ignition, feel it again, turn on the usual stuff and see if/when it gets warm.
Turn off the whatever makes it warm.
Now start looking for that short.

 

[Selahdoor]

Wait.

You took the grounds off the batteries, and it would still turn over?

 

[Noiseydiesel]

Mebbe that lack of a good ground made a nice power surge to fry the link. . . .
uh, oops?

 

[Poorman]

The only fusible link I can find is on the wire coming off the selonoid, it's the type that is a little sealed green box and says "fusible link" on it's top. I thought these were either good or bad, is it possible for one to work intermittently??That wire does appear to feed everything because removing it shuts everything down.
I just looked and there is a small wire that attaches from one battery (ground) to the frame. I think thats why I got the starter to turn over. I only tried that because I wanted to test the theory that a poor ground connection could shut everything down like what I have, I've read that in several archived threads, but now I don't think that is possible because if a disconnected cable doesn't shut things down I don't see how a poorly connected cable could.
Again, everything is working fine right now, which makes it hard to know whats wrong but it's shut down twice so I know somethings not right. Thanks

 

[IDIBRONCO]

It may not be the same for our trucks, but I had something similar happen to my 84 Mustang one time. I had eaten lunch with a friend and we were in my car heading back to work. I tried to take off from a red light and the car died. We had to pus it through the intersection since it had no power at all. I kept the key in the start position while he wiggled things under the hood. When he moved the starter solenoid, it was loose, but got a ground again. I drove back to work without farther issues. After work, I wanted to make sure that it didn't happen again. One of the mounting screws for the solenoid was missing because the hole stripped out. I ran a separate ground wire from the remaining mounting screw to the fender. I never had another issue with it again and I drove the car for another 4 years or so. It may worth looking at or even running a similar ground wire to your fender mounted starter solenoid.

 

[riphip]

Look over the top of the passenger valve cover for large yellow cables that meet at a connector with 3-6 wires in it. Probably burnt inside the connector.

 

[franklin2]

You have a lot of fusible links over there. But only two, J and M could cause your total blackout.

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[Poorman]

Thanks idibronco On mine the always hot stud on the solenoid acts as a connector for several wires including the wire that seems to power everything up, your comment did prompt me to look deeper for loose grounds, only thing I found was a small wire going to ground under the dash that had been chewed thru by a mouse, but it was dangling free and right now everything is working normal so I don't suspect that as the problem.

 

[Poorman]

Riphip, I could only find one large yellow connector and it looked good.
Franklin, yes, disconnect the wire with the j fuse and it mimics my problem ,it's hard to know which one is M, there are several in a bundle in that area. these fuses look clean with no heat discolor. Would that fuse go out and come back on twice like mine did, it's on now or i would just jump around it. If I replace it I'll never know if that was the problem and I'll forever be nervous at intersections. One thing I haven't mentioned is that the first time it went out the key felt a bit gummy when turning, like it was in cold grease, but it was 90 degrees out, it was one of those things that you question later if you really felt it, or was it just different because the usual clicks weren't there. Thanks for taking time to think about this!!

 

[CDX825]

There is a large yellow wire that feeds power to two fussible links on the passenger side fender. One is lighting power and the other is ignition power. If you have no power to the lights and no power to the ignition switch its that yellow wire.

 

[Poorman]

Thanks cdx825, that would be fuses L and M that Franklin referred to. I probably need to open up the wires from those fuses down to the solenoid and look for damage, Thanks

 

[riphip]

Also, look on the back upper right of the fuse block under the dash. My '86 melted the yellow power wires a long time back

 

[Poorman]

I think I solved the problem! Riphip and cdx825 you led me to it. At first inspection everything on the passenger side fender, the big yellow and the split into the fusable links looked good, but it made since that it had to be in that area. So I pulled the battery and moved some things around to give me a little elbow room. I started twisting on the big white connector right before the two fusible links and the dome light started flickering. When I finally got it apart the hidden inner piece had a lot of heat damage, it had even melted and cracked the plastic, I was amazed at how the outer housing looked like new but inside was toast. I cut it out and wired it solid and also replaced a length of the fusable wire that had some damage from a mouse. I'm 99% sure that was the problem but just for a piece of mind I left all my jumper wires in place just in case. Thanks to all of you!!!!

 

[riphip]

Great News!! Glad you got it going. I think that is the route most of us with the early year trucks do. That connector is a problem.