Fuel pump?, injectors?, or starter?

was having trouble cranking over 2002 express 1500 cargo van 4.3l v-6. acted like a fuel filter problem or clogged injectors so upgeaded fuel,added injector cleaner and then changed fuel filter. Ran ok for a couple of days then was not started for about 3 days. Went to start and it was back to cranking but not started…starter was cutting out every once in awhile while cranking but still not starting. Replaced the fuel pump and starter relay…no change…no start. Saw online that new crank sensor fixed the problem for others…i changed the sensor…cranked it for about 15 seconds…still no start…then while cranking the starter stopped and it was as if the battery went dead…the engine panel lights just barely light up…flicker…and nothing happens when i turn the key…but the door chime still sounds but i dont hear the fuel pump priming…how bad did i screw things up?

See if it will jump-start when connected to a running vehicle…Sounds more like a failed battery, plus maybe something else. When you get it to crank, try releasing the key after a few seconds, then try again. I have two vehicles that like to start on the second try for some reason…

If it STILL wont’s start, dump 1/2 ounce gasoline into the air intake or try starting fluid. If that works, you know it’s a fuel delivery problem. If not, check for spark…

I don’t see where anyone has checked or replaced the battery or battery cables and cable connections.