did you download the service manual form hemitruckclub.com? that should provide you the wiring, and fuse locations if any. You should have a relay & a fuse located in the fuse box... swap the relay with another as they are the same p/n and go from there. Also, you could have a bad ground going to the pump. when you measured the voltage was it across the connector or was 1 side to the frame?

 

DAMN .... you guy's sound like the CALVERY !!!

LOL !!!