Location
Y643 | Quantity control valve |
W07.05-1005-76
The quantity control valve (Y643) is located on the high-pressure pump.
Task
The quantity control valve (Y643) has the following tasks to fulfill:
Control of the fuel inflow in the fuel system high pressure pump
Discontinuity of the fuel supply in the fuel system high pressure pump when stopping the engine
Function
In order to achieve a high hydraulic efficiency of the system, only the fuel is fed through the quantity control valve (Y643) of the fuel system high pressure pump (and therefore the fuel high-pressure system) which is consumed by the injection, inner leakage and controlling of the system. This is realized through throttling of the volumetric flow rate by means of changing the cross-sectional area at the control plunger inside the quantity control valve (Y643). The quantity control valve (Y643) is an electrical regulation valve. There is a force applied to the control plunger over the coil and therefore the cross-sectional area for the fuel flow rate changes. The electrical energization of the valve varies between 0 and 2.3 A dependent on the operating condition of the engine, and takes place over a pulse width modulated signal. Using the overlayed pulse width modulated actuation (dither) the valve is constantly held in movement with the goal of eliminating the frictional forces and thereby achieving virtually hysteresis-free operation as well as to avoid jamming of the valve. The quantity control valve (Y643) is open when deenergized.
To switch off the engine the quantity control valve (Y643) is actuated electrically and thus interrupts the fuel supply in the fuel system high pressure pump. For diagnostic purposes the quantity control valve (Y643) is still actuated electrically for some time after switching off the engine.