i have a 97 Dodge 3500, 4x4, auto, with cummins diesel. it all at once started missing on #2 cylinder. it had been setting for a month or so.
But i changed fuel filter , supply pump, ran treatment through it, changed the injector in
#2. nothing seems to worked. when i try to prime it up at supply pump. i hear air, but cant determine where its coming from. i have already removed the fuel heater. Any ideas.

 

It sounds like there is a hole somewhere
what is the conditions of the hoses around the lift pump?

 

Have you pulled valve cover on #2 and checked to make sure rockers are moving? What about a compression test on #2?