'91 F150 6-Cyl Manual
I had been driving for about 2-1/2 hours yesterday and stopped to buy gas. When i was finished pumping gas my battery didn't have enough charge to start the engine. Tried several things but no luck. Jump started the truck and it started on second try. This morning my truck started no problem. Never had this problem before or any other starting problems. Battery is about 3 months old. The one thing I have noticed lately is that when I drive for more than 30 minutes my battery voltage gauge on the dash gradually climbs until it gets to the L in NORMAL (Usually starts out around the M). I haven't got and reading with my multimeter yet but was wondering if anyone has had a similar problem. Not sure if battery is going bad or alternator wasn't charging it properly or what.
-Clayton

 

check all of the cables and connections. also the grounds . some times the cables on the starter get dirty or lose.

 

Also check your belt. I had a similar problem and it ended up being the belt was stretched out. It would work fine until after about 30 min then the guage would jump and the batt would die once I stopped and shut off the truck. For me I had put a brand new belt on a week prior and it was a deffective belt.