freelander fuel pump problem

hi I have a freelander td4 03 reg the fuel pump is noisy and I have replaced it with another second hand one and this one is noisy and stopped working with in 5 min of it being changed. I have tested it and put 12v to the pump and there is nothing coming from the pump at all I have also tested the wire feed to the pump and it goses to 12v for a while and then down to 6.96v and stays there I'm abit baffeled can you help pls as use it for my job delivering parcels thankyou. I am new to landyzone and I'm ian 42yr old