I need some advice on where to start looking. My 04 F150 5.4L Screw quit running a week ago. I thought it was the fuel pump as I had no fuel pressure. Once the tank was removed it was discovered that the pump was fine but some repair had been made to the wiring by the previous owner. The pump is not getting enough power to pump. The cut off switch has passed it's test so it is not there. Is there a common place I should be looking for a voltage drop? Please let me know any thoughts as I am going nuts and want the truck fixed.

 

Check the relay under the spare tire. It rusts out and then shorts out.

 

Thanks! The repair shop confirmed it was totally rusted out. However they are in short supply and now they need to find one. You saved me a lot of money in diagnostic time I am sure.