Ok not a Marine Diesel
mech... But I've got 220K miles on my VW TDI.
Kubota 4cyl tractor.
I've helped my neighbor with his Albin 2 cyl Diesel. Easy peasy thing to work on I've ever seen!
The thoughts are for me when/if there is a starting issue.
1) fuel flow.... "Verify" test for flow, no air in the lines, no water
in the lines etc etc etc.
2) Preheaters... "verify" if you have them. If so, verify draw and measure against either the known draw or one against the rest. If you have them having spares arround that are Known good (measure them and compare to the readings on the ones in the engine)/ Swap and use.
... if you have a manual crank, take the injector out and measure pressure with guage, compare to new/cyl to cyl (balance) by cranking manually to TDC.
4) check for water
in the block and the water pump for a leak...if you find sludge in the case (water foam) and no leak in the pump.... ooooops, better think about a re-engine. But pull the head
and check for a head
crack vs a block.
Diesels are easy/simple principal engines. They shouldn't take all that much time to start if you have, "heat" (pluggs), Proper fuel pressure and good injectors, compression. A little smoke at start up is normal.
I'd say give it more fuel and air as. Some "Require" priming. The Albin does, but runs like a Champ!