could it be a main relay rather than the fuel relay??

also check your earths, im guessing you have already though.

You said in the first post that the pump doesnt prime on ACC, it should only prime when in the ON position i thought, not ACC.. im sure thats what you meant though..

ummmm. trying to think of other possible faults. So you tested the pump and it seems ok??

If you have another pump spare you should try that.

My moneys on a wiring issue rather than a mechanical issue though..