Electronic control of the electric fuel pump
In the "Electronic control of the electric fuel pump" system, the electric fuel pump is activated on demand. The DME control unit or DDE control unit calculates the volume of fuel required by the engine at each point in time. The required total quantity (fuel) is sent to the electronic fuel pump control module (EKPS) as a message via the CAN bus.
The electronic fuel pump control module (EKPS) adjusts the power of the electric fuel pump, thereby ensuring that the electric fuel pump delivers the exact fuel quantity required. In conventional systems, the electric fuel pump is operated constantly at the maximum number of revolutions with the maximum available vehicle voltage. In each operating status, the maximum volume of fuel that could be required is available.
The "Electronic control of the electric fuel pump" system optimises the fuel supply and lowers fuel consumption. The "Electronic control of the electric fuel pump" system is available for petrol and diesel engines.
The "Electronic control of the electric fuel pump" system includes the following functions:
- Supply of fuel in line with requirements
- Diagnosis of low pressure fuel system
- Emergency operation (complete activation of the electric fuel pump) in the event of problems in communication with the CAN bus.
- Cooling and lubrication of the electric fuel pump and high-pressure pump (diesel engine)
Example of functional networking F01
|1||Central gateway module (ZGM)||2||Crash Safety Module (ACSM)|
|3||Car Access System (CAS)||4||DME (Digital Engine Electronics) or DDE (Digital Diesel Electronics)|
|5||Junction Box Electronics (JBE)||6||Electric fuel pump fuse|
|7||Electronic fuel pump control module (EKPS)||8||Fuel level sensor|
|9||Electric fuel pump||10||Fuel level sensor|
|11||Instrument panel (KOMBI)|
Control unit variants
Various electric fuel pumps can be operated with the electronic fuel pump control module (EKPS). To do so, there are the following 2 control unit variants:
- Direct current (DC) version
- Rotary current (AC) version
With the direct current version, the electric fuel pump is driven by a direct current motor with permanent magnet. With the rotary current version, the electric fuel pump is driven by a brushless three-phase motor with permanent magnet. With the corresponding encoding, it is possible to operate various electric fuel pumps with the relevant variant of the control unit. The two control unit versions are distinguished visually by the colour of their connectors: The direct current variant has a maroon connector, the rotary current version has a white connector.
The electronic fuel pump control module (EKPS) is permanently connected to terminal 30g_z (BN2000) or terminal 30B (BN2010) and only requires a low standby current when it is not active.
Types of control
To ensure the fuel supply, engine control sends a message with a demand request to the electronic fuel pump control module EKPS via the CAN bus. Depending on the type of electric fuel pump control, this message describes the setpoint value of the delivery rate (speed control) or a specification using pulse width modulation (pressure regulation).
In the case of speed control, the engine management system sends a message with a requirement request across the CAN bus for the volume of fuel in litres per hour. This value is converted on the basis of a characteristic curve in the EKPS into a desired speed and this speed is set.
Pressure regulation involves voltage control. By comparing the current pressure in the feed line to the high-pressure pump with the target pressure, the engine management system sends a request signal across the CAN bus to the EKPS. The EKPS converts this request signal into a nominal voltage. Taking account of the currently applied voltage at terminal 30, this specified voltage is converted into a pulse duty factor (pulse width modulation) and set.