Lull 944E42 that won't run after bad fuel

We've got a Lull 944E42 with a Cummins diesel engine that was running rough last week (sputtering and stalling) then wouldn't start. After looking at the fuel it was pretty dirty and so was the fuel filter. All changed, tank drained lines blown out. New fuel and filter and now it won't start. Had mechanic come to job site and he was able to get it to run on ether. He could see fuel up to and past filter and could see fuel after injector pump. Injector pump raises pressure to 1600psi? Injectors pop open at high pressure? I'm no mechanic, but I know the basics and can follow the conversation.

He's suggesting new injectors and if not that then new (or rebuilt) injector pump. He's skeptical that 4 injectors would all be bad at same time.

Just wondering if I could point more definitively at the injector pump at this point. Really trying to cut down time as I need this machine working at critical point in build. Based on everything I saw It looks like pump to me. They have ordered injectors but not pump and I think that is wrong direction, we should have pump ready to go.

Ideas / comments / suggestions...

Thanks,

Roveer

Lull 944E42 that won't run after bad fuel