Ive just read the previos posts in this thread which I should have done to start with. Diesels need two things to run, Fuel and air. Black smoke means too much fuel for the amount of air its getting. Remove the air cleaner element and run the engine again, (I dont care how new the element is) check all the air passages for obstructions. ( You woudnt believe what I have dug out of air intakes over the years)

You said that you have adjusted the tappets, make sure you got this right mate. Its easy to stuff it up, (been there, done that). make sure the timing marks on the injector pump flange are aligned. (Injector pump timing is normally set for life)

See how you get on.

Cheers