I have a 1983 300D non turbo, my first project car, and I was starting on the easy stuff by doing a diesel purge and fuel filter replacement. Everything went fine and it really was pretty easy. Then, it started for a few seconds and then died.
I pumped it until the filter was full, and it was actually sloshing out from the pump, which concerned me. Not sure if that's normal but it seems like it shouldn't be.
Not sure if this is a common problem but I didn't see anything on this forum (maybe it's there and I just didn't go through enough search pages), but my solution was to turn the car around so that the front end was lower than the back. Apparently gravity did the trick because it started right away.
Anyway thought I would post this in case someone else has the problem; it was a lot easier than disconnecting a bunch of stuff.

sloshing out of the pump----you mean the hand pump. and this also means its the old style white t headed hand pump.
the good news its still operating from what you describe==sloshing out.
did you remember to screw it back clockwise to tighten that handle shut?

the newer style updated handpump does not unscrew counter clock and rescrew to tighten back. if you did not retighten that handle it is sucking air thru that old stype pump.
I just swapped out that piece for a newer style one--it gave me a hell of a lot of trouble a week ago.

Yes I did tighten it. One day I think I will replace it too. But it's at the end of a long list. Lol.

If the old style priming pump is leaking, you will need to move its replacement higher up on the list. Eventually, it will cause so much air to get into the fuel system that starting issues will be prevalent.

__________________
Sam

84 300SD 350K+ miles ( Blue Belle )