1987 F-150 XLT Lariat 280,000 miles
i've been having this problem for a while. I can never turn my car off if i know i am going to be getting back into it in 5 minutes beacuse if i shut it off it wont start. in the morning it starts ok, but it starts rough. i dont know how to describe what it's doing but it sounds like its gasping for air or gas. i did run the truck dry so that could have damaged the fuel pump. but the main problem is that it wont start when the engine is hot. could the addition of a sound system be causing this? any help is greatly appreciated because i need a reliable car!

p.s. the battery shows 12.5 volts so it couldnt be that...