Another possibility (because I had this happen to me 2 years ago....) is that your lift pump went out. I changed my fuel filter, filled it up and went to crank the truck and it wouldn't start. There were no leaks, vacuum or otherwise. My fuel pressure gauge showed 25-30psi before changing the filter with no issues driving. After running through everything, a friend of a friend that runs a garage mentioned that he had a 12v cummins lift pump 'go out' during a filter change one time before. I had 287k on the truck then and thought 'what the hell, why not'. Well, wouldn't you know, a new lift pump put on and the the truck fired right up (basically...). So if you think you're doing everything correctly, no leaks, and you're over 250k on your lift pump, you might want to change it out. My only explanation for it is that when the system lost it's prime, the failing check valves in the lift pump came to life. Looking at the original lift pump, that seemed to be the only problem - two of the check valves weren't very checky! Priming using the plunger was unaffected and I could prime until the cows came home and it still wouldn't start/run until I changed the lift pump.