Fuel Pressure Regulator

Fuel pressure regulator is integral part of throttle body. Pressure regulator has spring chamber that is vented to same pressure as tip of injector. Because differential pressure between injector nozzle and spring chamber is same, only the length of time that injector is energized controls volume of fuel injected.

Fuel pump delivers more fuel than is required by engine. Excess fuel goes to fuel tank from pressure regulator via fuel return hose. Fuel pressure regulator function is mechanical and ECU does not control it.