This has somewhat been covered already.
There is actually 2 sections of the Fuel Injection System that may need to be cleared of air; depending on what type of work you did.

To clear/bleed the air out of the Fuel Supply system you use the Hand Primer (if you have one). This bleeds/clears the air out of the Low Pressure Fuel Supply part of the system where all the rubber and plastic hoses are connected to to include the IP housing and 2 Filters. (typically needs to be done after changing Fuel Filters or Fuel Supply Hoses.)

If you have Run Out Of Fuel, or have not bleed the air out of the Low Pressure system well before cranking the engine or have Removed your Injectors you need to also bleed/clear the air out of the High Pressure part of the Fuel Injection System which is from the IP Delivery Valve Holders through the Injector Hard Lines and up to the Injectors. Air trapped in the Injector Hard lines will compress and very little fuel will move in them witout an extreme amount of cranking the Engine.

This is done as previously stated by leaving the Injector Hard Line Nuts up where they thread onto the Injectors threaded on but loose and crank the Enignie until you see fuel comming out of all of them and tightening them afterwards and starting.

The newer model Mercedes Diesels have no Hand Primer to bleed the air out of the Fuel Supply System, it is supposed to be self bleeding. All you can do is crank the Engine and hope your Starting System is up to it.
However, if you Ran Out of Fuel or have worked on your Injectors you still may need to bleed/clear the air out of the High Pressure part of the system.

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84 300D, 82 Volvo 244Gl Diesel