Hi Hi Current,
All I can suggest is go back to basics, check the glow plugs, check the fuel filter, choke the engine and give it a 'tiny' prime, flick or electric start and listen/watch what happens. The worst thing you can do it 'flood' the engine as the bottom 2 cylinders will hydrolock and then you need a rebuild, try taking the plugs out, spin the engine up with the electric starter till fuel is seen making it's way to the engine. Then stop, put all the plugs back in and try starting it again - choke on and mid throttle see/listen to what the engine is doing and adjust accordingly.

Good luck, looks like a nice engine.