Fuel Pressure Regulator: Description and Operation

Typical Fuel Pressure Regulator:

The fuel pressure regulator is attached to the fuel supply manifold assembly downstream of the fuel injectors and regulates the fuel pressure supplied to the injectors. The regulator is a diaphragm operated relief valve in which one side of the diaphragm senses fuel pressure and the other side is subjected to intake manifold vacuum.

The fuel pressure regulator is controlled by the manifold vacuum and will always maintain fuel pressure at a constant value above intake manifold pressure. When intake manifold vacuum is low (fuel demand high) spring pressure inside the regulator causes the valve to partially close, which increases fuel pressure in the fuel rail. When intake manifold vacuum is high (fuel demand low), vacuum acting on the diaphragm compresses the spring, opening the valve further. Return fuel flow increases, resulting in lower fuel pressure in the fuel rail.