I have a 1991 F250 7.3L Diesel that has decided to stop starting... hopefully, someone here can make some suggestions. When I try to start the truck, the solenoid clicks once and then everything electrical dies. I had the starter bench tested at AutoZone and they say that it is fine, as are the batteries (tested also). I connect the two battery wires to the solenoid and leave it hanging rather than connecting it the fly wheel... one solenoid click and nothing. I replaced the stupid "Ford" solenoid on the fender of the truck (I don't know why Ford insists on two solenoids but that can be for another post) - one click solenoid and nothing. I took a jumper cable and went between the + post of one battery and the corresponding post on the starter's solenoid... this time I get one solenoid click, a few (5-6) cranks and then nothing. The wire on the jumper cable heats up and starts melting the plastic sheath (I think if it was heavy enough gauge that jumping the battery to the solenoid would work). My dad tells me to check all the cable connections (+/- wires)... I checked and cleaned all the (+) connections with a wire wheel on a grinder or sandpaper so they are all clean (bare metal). I didn't check or clean the engine or frame grounds because I think that if I had a ground issue, my battery to starter solenoid jumping would produce the same results as without the jumping... I did nothing to the ground when I run the jumper cable. My next option is to replace the battery cables... I call Ford and they want $300 for the cables (are you f-ing kidding me? I understand copper is expensive but how does the dealership justify that price?), AutoZone wants $110... note about the cable; the (-) cables are pretty standard, the (+) cable is connected to the left-hand battery, runs to the right-hand battery, and then splits. From here, one wire (16 gauge) goes to the "Ford" fender solenoid and then goes to the starter solenoid; the other wire (4 gauge) goes to another post on the starter solenoid. I am going to wait until Tuesday to see how much a battery shop can make the cable for me, but before I do that, am I missing something that I can check or change? Could my jumper between the (+) on one terminal to the starter solenoid really work if I had a ground issue? Again, when I do this, all the battery wires are connected as they would be from the dealership. I generally drive the truck to tow my boat only; this all happened when I took it for a drive (ran about 20 min) and then turned it off outside of a store... hasn't started since.

 

Auto or Standard?

By everything 'dies' you mean 'ALL' electrical power distribution fails?...

The fender mounted solenoid is nothing more than a 'large' starter relay for a higheramp conversion for the starter mounted solenoid.. Good cables are a must for the 7.3 for the amount of starter draw alone, as are good connections/grounds.. Bench testing a 7.3 starter may not yield you an actual/accurate test.. Total Amp draw taken off the battery cable during cranking/load is a better test/indication of a good starter, as these starters can heat up'quickly' if drawor load is too high which wouldn't show up on a bench test, and may make for a harder starting engine as well.. Tends to heat the battery cables quick too.. Although it doesn't or maynot explain your short crank times.. If your loosing all battery power, then the cabling must be suffering a drop out from a bad connection/s.. If all the cables/connections are good, and/or you replace them with no resolve, then first thing to check would be the small connection on the starter relay (fender solenoid) with a test light/meter for a good voltage during a start attempt with NO drop outs while cranking or at least the ignition in the crank position.. This would eliminate a possible ignition switch, trans range switch/sensor problem.. If the starter relay proves out with a good voltage, then the next direction would be the solenoid/starter.. Since you said Autozone checked the starter without a load, then you jumped it with wire heating issues and only a few cranks raises a flag here.. Especially if you jumped the starter mounted solenoid only with a good hot set of batteries, good ground on the starter eliminating the relay and system with.. Also, the early 7.3's used to like to burn the engine/main harness connector on the right/passenger side due to glow control/draw..Won't make for a no crank, but something to watch for..

 

I know you said you did'nt think it was possible that ground was problem, but it is exactly what I think your problem is. Think about it. Your jumper wire got hot because completing the circuit required more juice through hot wire because ????? ground could not give good path.

 

Hi. I would check the connections as your dad had said. If your loosing everything,lights-interior/exterior,accessories,sound like a bad/corroded connection. Pull all battery terminals,clean post and cable ends. Check wires to solenoid on inner fender,all power runs from there. Check your block and body grounds.
Good luck,Dave