Help with a 2250

[simon999]

Were his plungers steel or ceramic? Did he replace tappets too?
I would pull pump head , take springs off the barrels ,put 40psi air into head inlet. Then check if plungers going back then you press them. They should go back by themself easy if not check valves in the head not working and need to replace head.
I would also run run with insite fuel pump rail leak test, to see how much pressure builds and do leak test. It should build about 29000psi. On my truck it drops only 20-40psi in 1 minute. How to do test is one of Rawze's videos:
https://youtu.be/eH9GRkeozTM