Citroen hdi fuel pump?

My xsara hdi stopped on friday just cut out on motorway. Been told it is likely to be the in tank fuel pump rushed around to get one yesterday one thing bothers me. Put 12v across the old pump and no life so think it is dead but on the connector to the pump I get 5v across two connections with the ignition on which I think is the sender and thought I should get 12v across the other two to fire the pump.Is this right and does it mean a relay or the ecu has a fault ? Any advice greatly appreciated.