John Deere PowerTech 6068 hard start

Here at Rafiki Rwanda we have a 120KVA generator powered by a John Deere PowerTech 6068T. A few weeks back it began not starting properly. The Autostart would engage and the motor would start for about 1 second then stop with an indication of Underspeed. After a bit of investigation, I discovered that re-priming the fuel system would enable the motor to start. Since then I have taken apart all the fuel lines on the tank side of the filter and fixed a couple of potential air leak problems. However, the problem persists and I'm now way out of my range of experience. My latest idea involves replacing the fuel supply pump as there may be a problem with the inlet check valve.

With no test equipment or qualified diesel mechanic in sight does anyone have any ideas of what I should look at?

Thanks,
Mike
Rafiki Foundation Rwanda

John Deere PowerTech 6068 hard start