Bosch LU Electronic Fuel Injection

Fig. 2 Fuel pressure regulator:

The fuel pressure regulator, Fig. 2, consists of a metal canister with a spring controlled diaphragm. The spring chamber is connected by a hose to the intake manifold chamber. Whenever pressure in system exceeds calibrated spring tension, excess pressure is discharged through the fuel tank return hose, maintaining a constant pressure differential between the manifold and fuel system.