[cheshired5]

The Euro 3 HP pump is a tandem pump so if you can fully prime the system with diesel by vacuum pumping the return line at the front of the engine, it should run fine.
That's why Diesel Purge is possible on a Euro 3 D5 but not Euro 4.

My in tank pump has been dead for a couple of years now.
I keep it above a quarter of a tank and the car runs fine so I wouldn't spend too much time on that for now.
Having a working tank pump is ideal but not essential. .

The fact that you had revving issues during the Diesel Purge does suggest air in the system.

You could clamp the rubber feed line into the HP pump and pull a vacuum on the return and it should hold vacuum or point towards where air is being allowed in/out.