Well, darn. If you can prime it and it gets hard to push, they'll usually fire up.
If we continue down the fuel path... Our trucks are getting old. If the filter head hasn't been rebuilt or replaced yet, it's overdue. I had to rebuild mine several (5?) years ago. Now, since some have experienced a crack in the filter head, I suggest replacing it. It seems like I saw some place had a new filter head with a Racor filter (the best!) for $120 or $140 (and it certainly wasn't a dealer!).
There are also some flexible lines that get soft and will collapse. I've even heard of the fuel lines rusting from the inside (my brother has an LB7 that did this).
Leaks or collapsing lines are very hard to find since air leaks in and diesel probably won't leak out. MIkey52 provided one method to test (gently pressurize the tank). Another is to add a lift pump (and more filtering while you're at it!). I added a Kennedy lift pump about 1-1/2 years ago to avoid these problems (or as some say, cover up any problems), but at least make it obvious where the leak is and keep soft lines from collapsing.
There are other things that can go wrong, but I've only read about them (crank position sensor, wiring to the CPS, FICM, etc.) but those are very painful problems, which I don't even like to think about. Hopefully, diagnostic codes would point to such problems.
2004.5 Silverado 3500 SRW 4x4, D/A (LLY), Ext. Cab, Long Bed
engineer837 aux rad, TxC CAI, LBZ MP, Scangauge II, Nicktane aux filter head, KD lift pump, 2008 PS pump, 2011 hydroboost, Frederico Swaybars, Rancho 9000XL, Torklift StableLoads, BFG AT/KO2, Lance 835 Camper often in the bed.