LR3/Disco 3
The HPP can supply up to 1600 bar fuel pressure continuously with short excursions to 1650 bar. Pump speed is 5/6
engine speed. However it is calibrated to deliver fuel pressure dependant upon engine speed and load and is always
under full control.
When the HPP is rotated, pressure is created when the VCV is open and the PCV is closed. The VCV and PCV are
variable position to allow variable fuel delivery and pressure control.
When the ECM actuates the piezo actuators, the rail pressure drop is off-set by additional fuel being delivered to the HP
rails by the PCV.
Pressure Reduction After Engine Has Stopped
The fuel pressure in the system is reduced within a few seconds after the engine has stopped as the PCV no longer has
the holding current it requires, and therefore opens. No residual pressure remains in the system and the fuel is returned to
the fuel return line (D) through the open PCV. The system is pressureless.
Function of High A Pressure Element
Fuel Induction
During the downward motion of the piston (3), a vacuum in the pump cylinder is generated, which opens the inlet valve (1)
against the force exerted by the valve spring. The fuel (A), which is flowing past the VCV, is sucked in. At the same time
the outlet valve (2) is closed due to the pressure difference between the pump cylinder and the HP fuel in the ring line.
Fuel Delivery
