Sounds like the tank sock might be plugged up.
First I would replace the fuel filter, then blow air into the line from the tank to make sure it is clear of blockage. If it still does not run properly then I would get a small clear inline fuel filter and bypass the stock filter. (This is not a permanent fix but a tool in trouble shooting the fuel system) if the truck runs fine with that filter then the stock base is messed up. If it won't hold fuel pressure or takes a long while to prime then your lift puml is down and needs to be replaced. Also check for any loose clamps and cracked lines.
Last thing I would replace is the injection pump. It's not a big job if your used to working on this trucks. If you do have to get the pump rebuilt I can recommend diesel performance in Memphis TN. The rebuilt my pump with great results, they rebuilt a friend's pump that I installed and truck runs great and I know a guy here cucvrus uses them all the time.
Let use know if you have more questions and if you get the truck going
