PERKINS 4236-just stopped

My Perkins just stopped , a mate started it up ran for 30 seconds then stopped, wont restart and there is fuel at the pump and none, it seems, at the injectors.
any ideas?
any advice?
Superb engine til now.........

if you crack injector nuts it squirts out fuel in pulses

No, fuel from injectors, but fuel goes into the pump??

either air ,or pump stops not opening to start with

Injector Pump shaft snapped. £400 refurb- fitted snapped again whilst bleeding. £400 refurb, fitted snapped again as turned over. £400 refurb, fitted, started screaming as we tried to bleed it. Shaft snapped again........... take to diesel man for another refurb.
in the interim, I fitted a £20 scrap pump bought from a chap on face book. Fired up straight away.... smoked but it worked. this pump has now been refurbished but I am too depressed to go and collect it.
Really.

Obviously a problem with the rotor and cams