Welcome to the forum!
Diesels are simple beasts at heart. They suck gobs of fresh air, get a little diesel squirted in and off they go. No spark required, just make sure that squirt happens at the right time (depends on the crank angle sensor).
First thing I'd do is grab the primer bulb and give it 3 or 4 squeezes. If everything is good, that primer bulb will get very hard in those squeezes.
If you can pump it a lot, there's air in your fuel line and the pump has probably de-primed. This could happen because you have a fuel line failure (crack, cut) or your fuel tank ran dry and some air was sucked into the line.
First thing I'd try is to pump that primer until it's as hard as a rock. Then try starting it again.