7.3 won't start cold or sits for 5 or 6 hours
 

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?

These are super picky about having enough juice, if it needs replaced replace it. If it still seems to be turning over slow pull the starter and have it checked.

Also in 18 years have you replaced the glow plugs or glow plug relay?

No I'm 18 years old, the truck is a 1999 and I don't know if they've been replaced or not. If it's plugged in to the block heater it'll start right up everytime, I can just replace one or two glow plugs if only one or two are bad right? But I'll replace battery as soon as I get paid.

You can replace 1 or 2 but I would replace them all, or at least the 4 on the side you open up. Get the battery, see if that helps. Then I would buy a relay, if that doesn't work put glow plugs in it. Glow plugs are about $80 and a relay is about $30. If you go to Napa get the GPR109 instead on the true power stroke relay. The 109 is the same thing just mounted at a different angle and its a lot cheaper

Alright thank you. Getting a battery this Friday I'll let ya know if it works

As crazy as this sounds your starter could be going bad as well, When I bought my 99 It cranked the truck but it took awhile to start, then one day it failed altogether. I was surprised when I put the new starter on the truck how fast it turned over it fired the truck right up, much faster!