I am in the process of replacing the fuel pump. I just wanted to see what power I had to the pump. I cut the pigtail off of the old pump, and plugged it into the power cord in the wiring loom to the pump. I thought I would have 12v to the pump. one hot, and one ground.What I found out is one wire has power all the time, Switch on or off,not 12v, but around 4-6 volt The other wire which I thought was the ground doesn,t do much Can anyone explain just how the power goes to the pump, or how to check the power from the two wires to the pump. Give me a Christmas present, Thanks, Stan

 

The pump only gets power during initial prime for a second or two, then after the engine fires. If you measure in between that time, you'll usually measure a garbage value.

You have to measure it during that brief interval when the key is first turned from OFF to RUN if the engine doesn't start.

 

Thanks for the reply. I checked my pump wiring, that is how mine works. Then after the engine fires, does the pump run all the time, and bypasses the excess back to the tank? Thanks again, Stan

 

Yes, assuming a return-style and no FPDM. I think that's what you'd have.