My 1999 powerstroke will not start unless plugged in.. If it sits for about 5 hours without plugged in it won't start, no I love this truck to death! But only being 18 years old and buying the truck myself and doing all work myself I really can't afford much major, battery lights on and a battery needs replaced, could it not be turning over fast enough? Glow plug relay looks brand new.. Any suggestions?

 

Get the Batterys tested and replaced if needed. If that doesent fix it try the gp relay. My 95 has a few bad plugs and does the se thing.