I have a 2000 dodge cummins. I just replaced the transmission control solenoid. I drove it for 20 miles came home turned it off came back 30 minutes later and tried to start it. It would crank but wouldn't start. The lift pump comes on automatically when I turn the key on. I've already checked all of the fuses and relays and they are all good. On my gauges it says I have 16 pounds of pressure and its getting fuel to the injection pump but I still have no idea what's not making it fire.

 

I had this exact same thing happen to me. I replaced the fuel filter and even replaced the lift pump even though it had been replaced a year ago. After much fusteration I spoke with my dad and he suggested the starter. So I Then took the starter to a parts store to have it tested and it was bad. I put a new one on and it started up. So I would start there and it doesn't cost anything to have it checked at a parts store.

 

Have you checked the starter solenoid fuse? Start there. If not it may be time to rebuild the solenoid. Very easy to do it takes longer to get it out of the truck than it does to fix it.