When the ignition switch is turned to ON, the VCM activates a relay that runs the fuel pump for 2 seconds, and then turns it off. This is a sufficient time to build up enough fuel pressure for starting the engine. After those 2 seconds, power to the fuel pump is controlled by a switch in the oil pressure sending unit that closes when oil pressure is at or above 15 psi. So once the engine is started, the fuel pump runs continuously as long as oil pressure is greater than 15 psi. This feature has the obvious advantages of 1) saving the engine by turning off fuel flow in case of a loss of oil pressure, and 2) shutting off the fuel flow in case of an accident that stops the engine, or even a rollover (as the oil pump, sucks air up-side-down). Also, in order to prevent vapor-lock, the VCM activates the fuel pump relay and runs the pump for 2 seconds after the ignition switch is turned off.