does the fuel pressure regulator on a 2000 2.0 zetec engine rely solely on the vacuum from the inlet manifold to open it or does the fuel pressure also play a part. for instance would it stay closed if there wasn't enough fuel pressure?? thanks in advance, dan

 

It's always the pressure difference that opens the recirculation outlet. fuel pressure minus manifold pressure. The later engines didn't have a pressure regulator though. Think they just controlled the the pump voltage.

 

It's always open, but closes up a bit to increase pressure when needed, ie accelration etc, it senses this change through vacuum, recirculating the fuel all the time keeps it cool.
tabetha