Fuel Pressure Sensor/Switch: Description and Operation

Fuel Low-Pressure Sensor

Fuel low-pressure sensor
The fuel low-pressure sensor is screwed into the fuel delivery line between both of the high pressure pumps.
The fuel low-pressure sensor monitors the pressure of the fuel in the supply line. The fuel is delivered by the fuel pump in accordance with requirements.
The fuel low-pressure sensor serves the electric fuel pump control unit (EKPS). The analogue output signal is evaluated by the engine controller.

Functional description
Strain gauge are used for detecting the pressure. A steel membrane equipped with strain gauge in the sensor is deformed by the adjacent pressure. The changes in resistance in the strain gauge are electronically detected by a Wheatstone bridge and evaluated. The measured voltage is then included as an actual value in the electric fuel pump actuation.







Structure and inner electrical connection
The fuel low-pressure sensor is connected by means of a three-pin plug connection.
The sensor is supplied with 5 Volts by the engine control.







Characteristic curve and setpoint values
The fuel pressure information is sent to the engine control across a signal line. The fuel pressure signal for evaluation fluctuates depending on the pressure. The measuring range of approx. 0.5 - 4.5 volts corresponds to a fuel pressure of 0.1 MPa (1 bar) to 1.1 MPa (11 bar).







Please note the following setpoint values for the fuel low-pressure sensor:

Size Value
Fuel low-pressure sensor 0.5 to 4.5 volts
voltage range

Fuel pressure measuring range 1 to 11 bar

Maximum output current 8 mA

Temperature range -40 °C to 140 °C

Diagnosis instructions

Failure of the component

If the fuel low-pressure sensor fails, the following behavior is to be expected:
- Fault entry in the engine control unit
- Emergency operation with substitute value

General notes
Diagnosis of the fuel low-pressure sensor is started as soon as the ignition is switched on. After that, the diagnosis runs continuously every 100 ms.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.