I recently bought a 91 F350 with a 7.3 N/A IDI with a ZF-5speed thats in excellent shape mechanicly with the only problem being the darn thing won't charge even with a new alt & external regulator. Lookin for alitle help, been through every wiring diagram I can find on Google and even went through pictures trying to find what in the world I'm doing wrong here but I'm completely stumped as I hooked it up according to my understanding of the diagrams I've found and this is my first diesel and the extra battery cables are throwing me off as all my early 90 gassers that I'm familiar with are completely different.

I don't have a voltmeter to test with or even the electrical knowhow of how to do that so if thats what it comes to that it's going to have to take the truck to a shop to get it fixed. But after some looking in the truck I found a cut L shaped 0gauge or so wire from the engine bay towards the trans/starter direction. I don't know if its a remnant of an old battery/starter cable that was for some reason left or if it was hit by a copper theif at the PO's house (they're terrible around here) and never noticed untill now. And was wondering if I'm just missing a wire and thats my problem.

The truck will run if you put a fresh battery in or jump it, or if you drift start it, and it will run fine untill you turn the switch off or remove the neg terminal off the batteries then it dies like the alt or regulator is bad. Anyway sorry for wall of text I'm just at my wits end here and have tried everything I can think of to no luck . Pics below, this is the how the wire have to be on the solenoid to work, it will also run if they are simply reversed. But any other combination and I get no power at all, no dome lights no nothing. Any advice would be greatly appreciated hell even a picture of the correct way to wire all that up to the solenoid would be great as I can't find a diagram that actually shows how all of it goes on there, I tried to copy the way my gassers are and got absolutely no power to anything and had to go back to this setup.

 

Thats the positive cable from passenger side battery to starter. This is the only pic of my starter solenoid that I have right now. Mine is a 94.

 

The first pic is what is left of the original battery to starter cable. It appears as if the wiring is in the right position in the rest of the photos.
ford used the starter rely on the fender for the power distribution point for the rest of the truck. Have you had the alternator tested to see if it is good? It would not be the first time a "new" alt. was bad right from the box. A mulit meter is fairly cheap, and can be a valuable tool. Without knowing what voltage the alt. is puting out it is kind of hard to help out.

 

Check and clean all your grounds especially the one on the regulator and make sure there is enough grounds...Motor to body to battery then spray some of the battery wax on all the connections to keep them from corroding, The ALT to REG wires.... The bat one goes to the solenoid hot side,S goes to S on the reg F goes to F, The light green with red line is the ALT light its really simple, But if its not grounded really good it wont charge.

 

Thanks for all of the responses yall, sucks trying to fix a electrical problem when the PO had someone who by the rewiring/rerouting I had thus far obviously didn't have a clue what in the world what they were doing. I'm no expert thats for sure but can atleast follow a diagram. I just wanted a fresh pair of eyes for a doublecheck to make sure as I couldn't find a diagram for the fenderwell solenoid and to make sure there wasn't something diesel specific I didn't know about.

But I think I fixed it, I finally had spare time today to do things right and went out today with a can of brake cleaner, a wire brush, and some extremely fine grit sandpaper and essentially white gloved every connector and where things were grounded and hooked everything back up and it seems good now. Need to add a real voltage gauge but the idiot gauge in the dash actually looks like its charging now, sits in the middle of NORMAL and goes up slightly with higher RPMS compared to where it was sitting between the N and the far left side never moving. I cleaned it all day before yesterday while I was hooking stuff up via diagrams but apparently didn't do a good enough job of it.

Thanks agian for the help!