Sounds like you got a"-"where a"+" should be...or the other way around.I added a new heavy duty ground from the engine block, passenger side to the inside of the wing. I did confirm all the other grounds were solid. Even after this, the wire continued to smoke upon attempting a start. I traded out relays but at that point it was too late as that ground had smoked through the plastic.
But I do agree, why would that have happened in the first place? Bad main ground somewhere, or open relay redirecting current when it shouldn't have?
And, to note, the instant I turned the key to start the truck, the smoke appeared. Check out the you tube video I had posted above. (HERE )