first start it cranks slow but if its not too cold it will start up. now i can run it for fifteen minutes and turn it of for four hours (the engine is cold again) and it will start up normal again. I was thinking batteries overnight might have a drain and the alternator charges them back up for the fifteen minute drive and even though its cold in the again it will start fine in the next few hours. does this sound likely give me some suggestions.

 

Does it crank slow after it sat for the 4 hours, or does it crank faster? My first guess would be a leak in the fuel system first, and losing prime overnight.

 

Either you have a drain or bad batterys.

Take it in with the batteries charged up and have them put a load test on them, this will tell you if the batteries are bad or not.

Heavy charging like you are having will toast your alternator.

 

it cranks faster after the initial start up as long as you don't wait 20 or 24 hrs.

 

get the batteries tested. My bets are on one going south. A bad one will also pull the good one down...

 

If one battery is bad go on and replace them both you probably have hurt the better one also.

 

You will also get a slower crank if the truck sits in the cold all night without the block heater plugged in