Fuel Delivery: XJS

The fuel pressure regulator maintains a constant pressure in direct proportion to intake manifold vacuum. This is accomplished by attaching a vacuum diaphragm to the regulator.

When the ignition is switched to "ON" position, but the engine is not cranking, the fuel pump will run for 2 seconds to raise the pressure in the fuel rail and shut off. After the engine has started cranking the fuel pump is turned on.

All fuel pump switching is controlled by the ECU. In case any of the injectors become faulty, this system prevents flooding by limiting fuel pump operation when the ignition is left on.