Fuel Pressure Regulator: Description and Operation

Fuel pressure regulator






The fuel pressure regulator is located at the rear of the engine in the fuel rail. It consists of a fuel inlet, outlet, vacuum port and internal diaphragm.

When the engine is under high manifold depression, the applied vacuum sucks the diaphragm of its seat, allowing fuel to return to the tank, resulting in a lower fuel pressure. This is necessary because the high depression will try to suck the fuel from the injector, resulting in overfuelling if the pressure remained constant. Failure will result in a rich mixture at idle but normal at full load, or a rich mixture resulting in engine flooding, or a weak mixture. Although the fault will not illuminate the MIL, faults caused by the failure may be indicated.