Fuel Rail Pressure Sensor On the Td6 engine, the fuel rail pressure sensor is screwed onto the end of the fuel rail. The fuel rail pressure sensor measures the current pressure in the rail and supplies a voltage signal corresponding to the pressure applied to the ECM.
FUEL DELIVERY SYSTEM – TD6 DESCRIPTION AND OPERATION 19-1-11 Fuel Rail Pressure Sensor Cross Section 1 Electrical connections 2 Evaluation switch 3 Diaphragm with sensor elements 4 High pressure connection 5 Retaining thread The fuel reaches a sensor diaphragm through the high pressure connection. There is a sensor element located on this diaphragm (semiconductor component) to convert the changes in shape caused by pressure into an electrical signal. The signal generated is sent to an evaluation switch via connecting lines, which relays the prepared measuring signal to the control unit via the connections. The diaphragm's electrical resistance varies when its shape changes. This change in shape (approx. 1 mm per 500 bar) created by the accumulation of system pressure alters the electrical resistance and changes the voltage of the resistance bridge which has a supply of 5 volts. This voltage is in the 0 - 70 mV range (depending on the pressure) and is increased by the evaluation switch to a range of 0.5 - 4.5 volts. The exact measurement of the rail pressure is essential if the system is to function correctly. For this reason, the permissible tolerance ranges for the pressure sensor are also kept to a minimum when the pressure is measured. In the main operating range, the measuring precision is at 30 bar, i.e. at approx. ± 2 from the final value. If the rail pressure sensor malfunctions, the pressure control valve is activated by the control unit's emergency function. M19 3569