08-12-2011, 08:42 PM
when my sis' batterys went in her superduty hers would spin really fast but would barely start. her passenger side battery was shot. 2 winters ago when my batterys took a dump mine would turn over really slow but didnt take much to fire it off. my driver side battery was shot. a diesel shop explained to me that the second battery on the drivers side is to help spin the engine over. and the main battery on passenger side runs all the electronics. doesnt make sense but may be true.
If you can't fix it with a hammer and a welder then your gonna need a new one!