Fuel Pressure Regulator: Description and Operation

Fig. 5 Fuel pressure regulator:

The fuel pressure regulator, Fig. 5, located downstream of the fuel injector on the throttle body, maintains a constant fuel pressure of 55 psi across the injector tip. The spring-loaded diaphragm in the regulator is assisted by vacuum in the throttle body above the throttle valve. As venturi vacuum increases, less pressure is needed to supply the same amount of fuel into the air flow. In order to fine tune the fuel pressure under all operating conditions, the vacuum assists in opening the fuel port during high vacuum conditions.