I'm not sure about relays but my pump that is in the tank is turned on by a switch that is located on the oil pressure line. ( mine is "T" in with the oil pressure sending unit). Oil pressure = 12volts to the pump.
1990 28' Georgie Boy, 454, 4bbl, Thorley Headers, Recurved Distributor, 8.0 mpg. RVM 76
CAMPING: WHERE YOU SPEND A SMALL FORTUNE TO LIVE LIKE A HOMELESS PERSON.