Hey guys I posted this in the diesel forum, but they really didn't go at the question i posted, so I'll ask here. I own an 86 f350 dump with the 6.9l diesel. The truck sat for about 3 years in a heated garage, we brought it out, changed oil, oil filter, and fuel filter and put new fresh fuel in it. obivoulsy, batterys were stone dead, so we hooked two cars to the truck and jumped it. Heres where my problems start. Let the truck sit and idle for ten minutes, went to turn on the lights, and the truck just DIED. We had to rejump the truck, let it sit agian, then we did it again truck was fine. Then as we drove around, the gauges would all go down to nothing, then come back up. Did that a few times. A few weeks later we took the truck out to get a load, jumped the batterys, and what happened was a few times the gauges went down a few times, came back up, and then the seatbelt light and buzzer would come on repeatedly. Finally, when coming home with a load coming around a corner, truck DIED. I mean absolutely died, no power at all. With truck moving, tried to pop the clutch a few times out of 3rd gear, nothing. Towed truck home, tried jumping it, but nothing happened.
Now, the day we used the truck to get our load, we put a battery from a small block chevy in the dump because we couldn't afford new batterys for the truck, figuring that at least one new battery would help. Guys, what could the problem be. The vehicle is not air bound, its getting fuel. Could it be that the other battery being so dead, its drawing power from the other good battery? Could the alternator be bad, because the truck obviously isn't holding a charge. I don't know what could be wrong, its a shame the truck is such a good truck. Sorry for the long post, but I need help!

 

The main problem is the dead batteries. They may be sulfated to the point they will never come back. When you jumped it and got it running, the dead batteries could have overloaded the alternator, blowing it. Also, when the batteries are extremely sulfated, the system acts like they are disconnected. The alternator isn't designed to run all of the electric loads without the battery(ies) in place. There might also be some other connection issues. If you can't afford new batteries, at least swap in two fully charged batteries robbed from other vehicles (hopefully your own). Then see what it does.