Fuel Pressure Regulator

The pressure regulator is a sealed unit which is divided into 2 chambers (fuel and spring chambers) by a diaphragm. The fuel chamber receives fuel through the inlet side from the injector fuel rail. The spring chamber is connected to intake manifold vacuum.

At idle, intake manifold vacuum is high. The diaphragm is pulled back by intake manifold vacuum. Any excessive fuel is returned to the fuel tank. As throttle is depressed, intake manifold vacuum decreases. The regulator spring overcomes manifold vacuum, increasing fuel pressure.

During hot restarts, PCM increases fuel pressure at injectors by sending a signal to fuel pressure regulator control solenoid valve.