Hi to everybody.

Could anybody help me please with my problem? My car is BMW 525TDS (April, 1993 year ). I know when I put the key on ignition ( not starting the engine, just switch on the key ) the electric fuel pump ( which is in fuel tank ) should work ( a short time ) to supply the fuel to engine ( before starting the engine ). It doesn't work. What could be the reason? I have checked the voltage on fuse N23 ( the pump's fuse. The fuse was OK ) and there was not a voltage when I switched on the key on ignition state. The relay which supplies the voltage to that fuse also was OK. I think that from a reason (I would like to know WHAT reason ) the DDE doesn't send signal to mentioned relay. Maybe by the some reason there is insufficient pressure in fuel supply system?
My thanks to everybody who will reply to my issue.