Fuel Pump Control Unit

Fuel Pump Control Unit







The fuel pump control unit is installed on the right in front of the fuel tank and has the task of stepless control of the electric fuel pump. This control unit receives the set point speed of the fuel pump from the DME control unit via a bidirectional PWM interface and sends back diagnostic information.







The control unit is connected to the vehicle electrical system voltage via terminal 30 and terminal 31 produces the connection to the vehicle ground. The output of the fuel pump is controlled by the DME control unit by a PWM control signal. This bi-directional PWM interface is also used for diagnosis of the control unit for the electric fuel pump.

The speed of the electric fuel pump is regulated by means of the specified frequency within the power limits of the fuel pump (with limitation of the phase current) and independently of the vehicle electrical system voltage (voltage compensation). The pump motor is a 3-phase synchronous motor without position feedback and without sensor. Further diagnostic information on the PWM signal and diagnosis is described in Guided Fault Finding.

NOTE: Starting of the electric fuel pump from 5 to 90% of the nominal fuel pressure must take place within 0.3 s at nominal voltage (12.5 V).