Changed the fuel filter on my buddys 06 lbz duramax and cant get it to prime. Never had this happen before. When pumping it wont build up pressure and just barely squirts out a bit of diesel. I tried closing the screw to try to build up some pressure and it still wont. Checked all the o rings. But the WIF sensor wires had been torn right out of the sensor by previous owner(he just bought the truck), and the sensor is pretty rugged looking. Dont know if that has anything to do with it.