Range Rover SE (LP) V8-4.0L (1995)
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Fuel Pressure Regulator: Description and Operation
Regulator Closed
FUEL PRESSURE REGULATOR
Fine tuning of fuel pressure (34 - 37 psi) at the injectors is controlled by a regulator valve mounted at the end of the fuel injector rail. The fuel
pressure regulator contains two chambers separated by a spring-loaded diaphragm. One chamber contains fuel from the supply line. The other
chamber is linked to the engine side of the throttle butterfly to sense manifold vacuum (negative pressure).
When fuel pressure and manifold vacuum are low (full throttle), spring pressure holds the diaphragm valve against the fuel return pipe. This
assures a higher level of fuel pressure to satisfy the fuel needs of the injectors. Fuel pressure must exceed a calibrated amount before the spring is
compressed and fuel is allowed to enter the return line.
Regulator Open
When manifold vacuum is high (idle and coastdown), the combination of fuel pressure and vacuum is able to overcome the pressure of the
regulator spring. The fuel return line opens at much lower fuel pressures when vacuum assist is present. This reduces the tendency of manifold
vacuum to draw excess fuel from the injector nozzle and ensures that the amount of fuel actually delivered matches the level desired by the ECM.
The fuel pressure regulator is pre-set during manufacture. No service adjustments are provided.
