2002 tdi fuel pump not working

I have bought a tdi 1.9l engine code atd that was not running, was told needed a new engine, anyway I got it home and thought I would have a look before buying another engine and the following is what I have found out.

The fuel pump does not prime when the ignition is switched on.
I have checked every fuse in the side of the dash and not one of them is blown, there are a further three fuses on top of the battery box and they are also fine.
I then got to the relays under the dash and non of them look or smell burnt and the one that I am lead to believe is the fuel pump relay does function when the key is turned to on but nothing at the fuel pump itself. I then decided to remove the relay and jumper the two main terminals and still no pump running.

I then checked with a meter to see if any power is getting to the pump in the tank and nothing. This includes doing the same test with the relay jumpered and still nothing at the pump connector.
The earth has continuity but there is no power.

I then put a separate battery in the back and powered the fuel pump directly from it and all works. At this point I tried firing the car up and it worked without issues, revs up and drives. Remove the battery pack and put the connector back on and the engine will still work but then eventually dies as the pump is not working, disconnect the connector and jump it with the spare battery in the back again and all works again.

All the lights on the dash light up on turning the ignition on and the glow plug light comes on and then goes off after a couple of seconds. When the engine was fired up with the pump running off the spare battery in the back all lights on the dash were out and there is no engine management light on.

From what I can find all I need to do is get power to the pump and this little car should be fine but I have now exhausted all my thoughts on the subject.
I can't find my cheap code reader at the moment so everything has been done sort of old school.

Any thoughts or pointers would be appreciated.

Well with no input I decided to jury rig the pump via a switched fused cable direct to the pump cutting the original feed wire out of the circuit.
Car runs fine without issue or any lights coming up on the dashboard, just need to make sure that the key is switched off and not in the auxiliary position as that would mean the pump running all the time when the engine wasn't.
This will have to do until I find the route cause of the problem and fix it correctly.