Fuel pressure regulator (BMW X5 E53)

The diaphragm-type fuel pressure regulator is designed to maintain a constant pressure of the injected fuel, depending on the vacuum in the intake manifold. It consists of a metal housing (1) (Fig. 3.24), a diaphragm (2), a spring (3), a branch pipe (4) for supplying vacuum from the intake manifold, a branch pipe (5) for supplying fuel, a drain branch pipe (6), and a valve (7).



If the fuel pressure in chamber "a" becomes greater than the force of spring (3), then valve (7) opens and excess fuel drains into the tank. Chamber "b" is connected by a hose to the intake manifold, depending on the degree of vacuum in which spring (3) acts on valve (7) in such a way that the pressure difference between chambers "a" and the intake manifold is always constant. As a result, regardless of the load on the engine, the pressure supplied to the injectors remains constant.