90 Quattro 20V (Canada) L5-2309cc 2.3L DOHC (7A) (1989)
Fuel Pressure Regulator Operation
Control vacuum is applied to a diaphragm which operates a pressure valve. When the engine is under very light load, control vacuum is high, spring
pressure against the regulator valve is reduced and the fuel system is regulated at a lower pressure. When the engine is under heavy load (as in wide open
throttle operation), manifold absolute pressure increases reducing control vacuum. More spring pressure is applied to the valve and fuel system pressure
is increased by the same amount as manifold absolute pressure, maintaining a constant differential under changing engine loads.