I have a 78 Ford F150, Before my truck will crank I always have to jump it off, it will run fine, then as soon as I turn it off, it has to be jumped off again, it's not the battery because I have went through plenty of new battery's, and it's not the alternator either, because I've bought that also, and it still does the same. I'm not sure what to look for from here, or what may be wrong, any suggestions or info would be nice, Thanks. (: