My truck died on me in the parking lot. I changed the battery because it didn't want to charge when I was trying to jump it. Then I drove for a little bit and then the truck died on me again. Thinking it is my alternator, I replaces my alternator and it is still doing the same thing. When on idle my RPMs are about 500-600 and the battery gauge is under 14. I am thinking that it might be my idle sensor but I have no idea. Also the check engine light is not on.

???? 6.0 L 6.6 L or the 8.1 L ????

6.0
I was told that I may have bad fuel in my truck, which is making my truck do this.

Gas can go bad if it sits too long, or if fresh gas is stored in a tank/container that previously held bad gasoline without being rinced thoroughly. If you're able to pull out a bit of it, you can check it. Bad gasoline tends to be more urine-colored and smells like varnish.

Might be the fuel pump going bad. Bought a truck of craigslist that would start, idle low, and stall out when put in gear unless you quickly pulsed the gas peddle. It was a '95 K1500, though, not sure if it is the same pump. Apparenlty these particular electronic pumps don't always burn out completely, like most fuel pumps. Instead, the amount of pressure they are able to deliver drops critically. They sometimes provide enough to get the engine started but not enough to run, throwing off confused gearheads.

Grad a fuel pressure kit from whatever autoparts store you can rent them from (most will let you return them for no net cost) and check your fuel pressure, first after the filter and before the filter if you are able to as well. Low fuel pressure can also be a clogged fuel filter.

Just a thought, no guarantee.