I misunderstood your first post.
If it doesn't start at all, and you have air in the return line from the IP, you probably lost prime and have air in the hard lines going to the injectors.

Re-establish prime - hook up a mini-tank with fresh diesel (or Lubro Moly, or ATF) - this bypasses bad fuel that might be in the fuel tank.
Use the primer pump to purge the air between the mini-tank and the IP elements (about 50 to 100 strokes will do it).
This won't remove air trapped between the IP elements and the injectors.

Try to start the car, if it runs...great!
If not, you need to bleed air out of the hard lines going to the injectors.
Loosen the hard lines at the injectors, unplug the glow plug harness and crank the engine (no more that 15 seconds each time with a few minutes rest between each time).
Fuel will eventually come out of the rearmost injector line at first.
(This can take a while and the battery may run down and need to be recharged...unplugging the glow plug harness gives you some additional cranking opportunities)
When fuel does come out of the rearmost line, tighten the fitting.

Repeat the above procedure until you have purged all five injector hard lines of air.
Plug in the glow plug harness, use the primer pump again, and then crank the engine and it should start.

If it doesn't start after re-establishing prime and purging air from the injector hard lines...then there may be a problem with the glow plugs and/or poor compression (a valve adjustment can help improve compression).

Also it's not a bad idea to have fresh fuel filters as well.
Let us know how you fare.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022