VALVE, Fuel Quantity Control: Operation: Operation

The PCM uses the Fuel Quantity Solenoid (FQS) and the fuel pressure regulator to control pressure in the fuel rail through pulse width modulation signal. The FQS is the primary actuated component used to control pressure in the fuel rail. During engine cranking the FQS is in the fully opened (100%) position allowing maximum fuel flow to the high pressure pump to help build fuel rail pressure quickly. During idle, and normal driving conditions the FQS pulse width modulated signal is adjusted to control the volume of fuel entering the high pressure pump to maintain the needed fuel rail pressure. The FQS is a normally closed solenoid. The FQS will default to the full closed position if the solenoid is de-energized.