Here are some oil pressure switches that have two contacts. One is closed when there is no oil pressure for an oil pressure light. The other is closed when there is pressure for a fuel pump.
However, I have switches that allow me to run the pump off the pressure switch, or whenever I decide I want to run the pump - like for test or priming, or never. But I have driven off with the pump not running, and the injection pump pulled fuel thru the supply pump and the frame mounted filter, and it ran fine. I finally noticed the pump light was off and turned the pump on.
And when someone says "it didn't need a relay", how many things do you say that about before they add up to enough to fry the key switch contacts? I have gotten all the high power circuits out of the cab - head lights, trans, fuel pumps,,,. I have added about ten relays.
https://photos.google.com/share/AF1...?key=YUhqcHFEXzBkZkx1Z0tOMDhTLU9laHRsbGlJZkdB