Glow plug preheating function (Mercedes-Benz Vito W639)

The glow plug pre-heating system is designed to achieve the required ignition temperature of the fuel mixture in the cylinder during a cold start. In addition, with economical fuel supply to the cylinders, it is necessary to increase the reliability of ignition of the injected fuel. Glow plugs are used for this purpose; they remain in a heated state due to the combustion of fuel.

The combustion chamber is preheated by glow plugs fed from the output stage of the preheating system. The duration of pre-heating depends on the coolant temperature. When the key is turned to position 2, the CDI control unit (N3/9) issues a command to activate the preheating output stage (A1e13) and to switch on the preheating indicator lamp (Ale 13) located on the instrument cluster. The duration of pre-heating is calculated by the engine control unit.

The preheating indicator light (A1e13) goes out when the preheating phase is complete

The information received by the CDI ECU is described in the description of the fuel injection start mode (see above).

The CDI ECU activates the output stage (N14/2), which supplies power to the glow plugs (R9/1-R9/4).