Fuel Pressure Regulator: Description and Operation

The EFI Fuel Pressure Regulator, is attached to the fuel supply manifold assembly upstream of the fuel injectors. It regulates fuel pressure supplied to the injectors.

The regulator is a diaphragm-operated relief valve in which one side of the diaphragm is exposed to fuel pressure and the other side is subjected to intake manifold pressure for multi-point fuel injection (EFI) and atmospheric pressure for single point injection (CFI).


The nominal fuel pressure is controlled by a spring preload applied to the diaphragm. By exposing the top side of the diaphragm to manifold pressure, a constant pressure drop is maintained across the injectors, for all modes of operation.

Fuel in excess of that used by the engine is bypassed through the regulator and back to the fuel tank.