new tow rig?!
Haha, maybe.
This vehicle had the EXACT same problem before I started tying stuff. It now has the new starter and battery, the alternator is new and once running it runs great. The frame is covered in surface rust (it was a Tahoe vehicle it's entire life) which is why I think it's a grounding issue. I picked up a Chilton Manual so as to chase down the problem. Input still welcome.