citroen hdi cutting out?

heres the deal , I bought a citroen c5 hdi yesterday , been mint all day , tonight I take the fuel pump out the tank to look at the gauge sender , put it back and it starts fine , get 10 mins up the road and the eml comes on and the car cuts out ,

I have to lock and unlock on remote to get it to start but the eml stays on , then it runs for a shorter time each time before it cuts out,

anyone know if the pump in the tank needs calibrating??,.