EDC starting function

W07.12-0037-10

Detecting start of injection

1 EDC speed sensor signal

2 Start of injection signals from needle motion sensor

A Start of injection after TDC

B Start of injection before TDC

The following subfunctions are performed during engine start:

- Detecting start of injection for initializing start of injection control by the EDC control unit.

- Controlling start quantity by the EDC control unit.

Detecting start of injection

After the drive switch is operated, the FMR control unit actuates the EDC control unit with an engine start signal (terminal 50) through the CAN interface.

As from this moment, the EDC control unit monitors the start of injection signals of the needle motion sensor. The positive speed pulse of the EDC speed sensor which follows immediately after the first start of injection signal (6 needle pulses/revolution are generated with the aid of 6 holes each 60° CA in the flywheel) is recognized as a reference mark.

With zero continuity of this speed pulse, a pulse counter is activated which blanks the superfluous 11 pulses until the next start of injection signal. After this, the control unit is able to control start of delivery synchronized to TDC.

Start quantity control

The start quantity is released by the EDC control unit once a lower starter speed is detected (signal from EDC speed sensor). The start quantity and start of injection are controlled in line with the coolant temperature (signal from coolant temperature sensor). If the engine does not start immediately, the start quantity is increased up to a certain maximum level.

 The fuel start quantity is set in line with the temperature in order to protect the engines from increased wear in the warming-up phase. As a result of improved starting characteristics at low temperatures, it is possible to do without a flame starting system in our climatic zone (coolant scarcely cools down to below 20 °C within a certain time).

Control signals from the EDC control unit to the control sleeve injection pump result in the fuel delivery being set and also the start of delivery by the fuel metering or control sleeve actuator.

Feedback signals to the EDC control unit are supplied by the fuel rack position sensor (delivery quantity signal) and by the needle motion sensor (start of injection signal).