Fuel pressure regulator

The fuel pressure regulator has constant vacuum. Changes to the engine RPM cause more vacuum to be applied to the fuel pressure regulator, allowing more fuel into the fuel rail or throttle body depending on the setup.

Rellnickuff, so I should not be able to pull vacuum through the fuel pressure regulator with the engine off or at idle?

Um, not quite sure what you mean, but this is how it worls. Fuel reg is closed nd not letting fuel into the fuel rail when the engine is off. When at idle, there is vacuum pulling on the diaphram causing fuel to flow through the fuel rail. When you push on the gas pedal, it revs the engine up causing more vacuum to pull on the diaphram letting more fuel into the fuel rail.

The vacuum pulling the fuel press reg has nothing to do with the reg itself, it is based on enigine speed and any vaucum leaks you might have in the intake.

Ok. I understand and that helped me alot. Thank you. Don White