The lift pump is not needed on these trucks, once running the IP will siphon enough fuel on its own.
If you do try what Crash is suggesting, pull the pink wire off of the injector pump. That way you dont suck air into the IP, and invite yourself for a day of fun bleeding the air out from all the lines.
Your issue is definitively a fuel supply one. It could be that the filter sock (more like mesh) on the pickup tube inside the fuel tank is clogged. On the passenger side of the frame, just to the rear of the front tire, there is the main fuel line running from the tank. you will want to pull the rear line out of the distribution block and blow ~5psi of air through it (REMOVE THE FUEL FILLER CAP FIRST!!!!) that will clear anything clogging the sock.
Then reattach the line. Pull the pink wire from the IP and bleed the fuel filter, Once you get the air out start the truck and see if you notice a change. Doing this is a temp fix, if it works you need to pull the fuel tank and clean it out.