Well after pumping the priming pump for what seemed like an eternity until I finally heard the buzzing noise and then pumping another full eternity, then cranking for about 30 seconds straight it finally caught and seems to run great. I'm letting it cool down now and see how another cold start goes.

I've never adjusted the valves on this so I think that's my next project and maybe a flush with the stuff at Diesel Giant.

I also need to replace my injector return hoses, as they're all weeping. Could that have been the cause of the air in the system (or whatever required so much priming)?

Final question: This is a W115 with an OM617 and I can't find any fuel pre-filter (the main filter is in a canister not a spin on), can I just add a pre-filter to this setup? Was there originally supposed to be a pre-filter?

Thanks again for everyone's help.