The P wire on the Carter pump is where the pump gets the 12vdc. On a positive
 OP switch the 12vdc could come from the OEM OP switch. The NAPA OP switch has 
three terminals, two 12vdc inputs and one 12vdc output. The one 12vdc output
 goes to the P terminal on the carter fuel pump. One 12vdc input is wire to a
 switched 12vdc source on the car so the 12vdc will be passed thru the NAPA OP
 switch to the fuel pump when the ignition is on and engine OP is above the
 switches baseline. This is for normal running operations. The other 12vdc 
input to the NAPA OP switch is from the car’s ignition start circuit. That way 
the OP switch and therefore the fuel pump get feed 12vdc during start up 
regardless of the engines oil pressure.