Fuel Presupply Control
Fuel Presupply Control
Fuel presupply control
The fuel supply for the M57TU2TOP engine in the country version USA equipment is ensured using a pressure-controlled system, in the same way as on the new N diesel engines.
Brief description of components
The following components of the fuel supply are described:
DDE control unit with presupply control function
The function of the fuel presupply control is integrated in the DDE control unit. The DDE uses the fuel pressure-temperature sensor to determine the current actual pressure in the presupply system. The DDE uses a number of input variables to determine the adjusting value signal factor to regulate the pre-delivery pressure. The pre-delivery pressure is regulated to a pressure of 4.8 - 5.0 bar (absolute).
The input variables relevant to determining the adjusting value are:
- Actual pressure in the presupply system
- Engine speed
- Fuel injection rate
The adjusting value is sent to the fuel pump control in the form of a CAN message. The adjusting value is sent in the unit l/h. The value range is 0 - 254 l/h.
Fuel pressure / temperature sensor
The fuel pressure / temperature sensor is located in the fuel feed line just before the high-pressure pump. The fuel pressure / temperature sensor measures the current actual pressure in the presupply system and sends the signal to the DDE control unit. For other functions in the DDE, the fuel pressure-temperature sensor also measures the fuel temperature.
Fuel pump control
The fuel pump control receives the adjusting value of the regulating circuit from the DDE as a CAN message. The value of the CAN message is converted via a characteristic curve into a voltage in the fuel pump control. This voltage is used by the fuel pump control to activate the electric fuel pump.
Electric fuel pump
The electric fuel pump is activated by the fuel pump control with a voltage of 6.5 - 15 V.
For correct monitoring of the power consumption of the electric fuel pump, an adaptation value is stored in the DDE control unit. The electric power consumption of the fuel pump at minimum activation is stored with this adaptation value. The lower limit value for monitoring the power consumption of the fuel pump is calculated with this adaptation value.
Fuel filter heating
The electric fuel filter heating is integrated in the fuel filter and is activated by the DDE control unit.
The fuel filter heating is switched on when:
- Fuel temperature less than 0 °C AND
- Current power consumption of the electric fuel pump greater than total of the adaptation value of the electric fuel pump and the offset value. The offset value is determined from a characteristic map and depends on the engine speed and fuel injection rate.
Notes for Service department
Diagnosis instructions
The control of the pre-delivery pressure is monitored by the DDE. Faults that occur due to control deviations are stored in the fault code memory of the DDE.
Activation of the electric fuel pump is monitored by the fuel pump control. Faults that occur here are stored in the fault code memory of the fuel pump control.
If the DDE control unit is woken by a wake-up signal, the EKP (electric fuel pump) control unit is not yet awake; electric fuel pump is activated briefly for around 10 ms.
When terminal 15 is switched on, the electric fuel pump is not activated. The electric fuel pump is only activated on actuating the starter motor.
Resetting the adaptation for electric fuel pump
If the following components are replaced, the adaptation of the electric fuel pump must be reset:
- High-pressure pump
- Electric fuel pump
The reason is that the high-pressure pump and the electric fuel pump have a major influence on the power requirement of the electric fuel pump.