Diesel Pump Not Working: Troubleshooting Guide

Hello, I'm having the following problem:

T4 AAB 2.4 Diesel, fuel injection pump failure.
Ordered a used one from a dealer, it arrived today, I installed it, set the start-up time, pre-filled the pump, started it, the motor runs briefly, then stops.
Everything checked: valve timing, fuel injection start, etc. Diesel filter, hoses, nothing.
What's noticeable is that the pump isn't drawing any diesel.
When I loosen the cap nuts on the injectors during startup, only a small amount of diesel comes out. The fuel line from the filter to the pump is empty.
Could it be that the pump is broken, or have I missed something? The pump should definitely be drawing fuel, right?

Poplar is stupid, at least today I'm only selling diesel.

poppel wrote:

...The line from the filter to the pump is empty. ...

Hello!

What does that mean EXACTLY?!
If it's "filled" with air, it's probably obvious .

Best regards from Munich!

The pump is naturally filled with diesel.
And the pump is broken.

Fill the filter and inlet hose completely. Fill the reservoir with diesel. Hang the fuel lines. Open the nozzle lines. If diesel starts flowing, close one or two lines and continue starting.

teileklaus wrote:

Fill the filter and inlet hose completely. Fill the reservoir with diesel. Hang the diesel tank high. Open the nozzle lines. If diesel starts to flow, tighten one or two lines and continue starting.

Or something like a small rubber bellows pump, like the ones that were originally installed on PSA engines, could be placed in the return line and operated until all the air is purged from the system.

Best regards, Rüdi.