I'm guessing he needs to bleed the system out. First bleed out the fuel filters. There should be a bleeder screw on the top of each filter. There is a bleeder screw on the injection pump, (I'd have to go look at mine to say exactly where right now) open that some, and then pump the hand pump lever until fuel squirts out of that. Then make sure all bleeders are closed, and that the injection line nuts at the injectors are loose for all 6 injectors. Open the throttle all the way, and crank the engine over until fuel squirts out of each nut at the injector. Stop cranking, tighten all the injector nuts, and it should start normally.

The air has to be bled out of those injector lines. Air will squeeze down in volume, preventing enough pressure from building up to open the injectors.

Hope this helps.