help with air in fuel lines disco 1

Hi all..... ive a 1994 m reg 300tdi disco and its air in the fuel n no matter what I do I cant get it out..... it starts fine.... seems to lack power..... things ive done are..... replaced the lift pump sender unit and run new fuel lines from the sender unit straight to the pump and back.... by passing the sedimeter..... I have clear fuel lines and can see the air in them ive tried to bleed it out n it wont bleed.... ive replaced all the diesel return pipes.... any advice would be appreciated thanks in advance

Sounds like air is being created at the input of the sender somehow.

Can you test the sender system with a bucket of fuel? See if it's producing air output?

I could do yeah.... but its a brand new sender unit.... it was only bought and fit this morning so would this be necerssary....? I can take it out though and test it no probs thanks