Fuel Pressure Regulator Assembly
WARNING: This page is about a different car, the 2004 Saturn Ion 3, 2004 Saturn Ion 2, and 2004 Saturn Ion 1. However, it is still accessible from the selected car via links, so may be relevant.
The fuel pressure regulator attaches to the fuel return pipe on the fuel sender assembly. The fuel pressure regulator is a diaphragm relief valve. The diaphragm has fuel pressure on one side and regulator spring pressure on the other side. Fuel pressure is controlled by a pressure balance across the regulator. The fuel system pressure is constant and is no longer a function of engine load or manifold vacuum. A software bias compensates the injector on-time based on the signal from the MAP sensor.