There is also the Fuel Pressure Relief/Overflow Valve. If that stopped holding pressure your Fuel Injection Pump will not get enough pressure to feed the Elements.

Replace the large Fuel Return Hosel (Cigar Hose) with a section of regular 5/16" Fuel Hose that is long eoungh for you to run into a Bottle (a cleal 1 liter Soda Bottle would be OK) to catch the Return Fuel. Start pumping on the Hand Primer till you get a good stream of Fuel coming out. When the Fuel is coming out good have someone clamp off the Hose with a Vice Grips or something else.

clamping off the Return Line means the pressure from the Fuel Supply/Lift Pump cannot be relieved and your Fuel Injection Pump is going to get pressure.
See if the Engine will Start like that. Only run it long enough to verify it will start. If you run it too long like that I would expect one or more of the little Fuel Return Hoses to come off or pop.
Anyway if it starts like that I would think that means the Fuel Pressure Relief Valve is shot or needs to have the Spring stretched to a 27mm Free Length.

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84 300D, 82 Volvo 244Gl Diesel