Engine start function

W15.45-0007-06

0 Ignition off

1 Drive position

2 Start position

3 Flame starting system warning lamp

4 Vehicle CAN bus

A4 Flame starting system control unit

R3 Flame glow plug

S1 Drive switch

Y5 Flame starting system solenoid valve

Operating procedure

1 Coolant temperature < –4 °C

2 The drive switch (S1) is in the drive position (1), tml. 15 ON.

3 The flame starting system warning lamp (3) in the instrument cluster comes on and the flame starting system control unit (A4) analyzes the coolant temperature signal supplied over the vehicle CAN bus (4).

4 The temperature signal meets the requirement for flame starting, which commences with the preglowing phase. The flame starting system control unit closes the circuit of the flame glow plug (R3). At the end of the preglowing phase, the glow plug has reached a temperature of approx. 1050 °C. The preglowing phase during a new start takes about 20 s, the time is less for a repeat start. The flame starting system warning light is on during the entire preglowing phase.

5 The flame glow plug is now maintained for 30 s at its temperature level for activating the start operation.

 The flame glow plug is pulse-controlled by the control unit for maintaining the temperature level.

-----------------------------------------------------------------------------------------

6.1 Initiating start process within the time specification of 30 s:

 The drive switch (S1) is in dirve position (2), the starter is operated.

 The flame starting system control unit actuates the flame starting system solenoid valve (Y5), atomized fuel flows through the fuel nozzle into the area of the heated flame glow plug.

 The fuel ignites and the flame heats the cold combustion air which flows through the intake passage, before it flows into the cylinders.

 As soon as the flame starting system control unit detects that the coolant temperature with engine running has reached 0 °C, the control unit thus interrupts actuation of the flame glow plug and of the solenoid valve and the flame starting operation is ended.

6.2 No activation of start operation within the time specification of 30 s:

 After the specified time period has elapsed, the flame starting system control unit interrupts actuation of the flame glow plug and ends the flame starting operation.

 An engine start which is commenced after this time period now takes place without flame starting.

-----------------------------------------------------------------------------------------

7.3 Engine start during the preglow phase

 If the engine is started within the preglow phase, the flame starting system control unit immediately switches off the flame glow plug. Engine start is then completed without flame start.