Glow Plug System: Description and Operation

Glow Plug System
The glow plug system makes it easier to start the engine at low outside temperatures. It is activated by the Diesel Direct Fuel Injection Engine Control Module J248 at coolant temperatures below 48°F (9°C).
The Glow Plug Relay J52 is activated by the Diesel Direct Fuel Injection Engine Control Module J248. The Glow Plug Relay J52 then switches on the working current for the Glow Plugs Q6.

Function
The glow process is divided into two phases, the glow period and the extended glow period.

Glow Period
The glow plugs are activated when the ignition is switched on and outside temperature is below 48°F (9°C). The Glow Plug Indicator Light K29 will light up. Once the glow plug period has elapsed, the Glow Plug Indicator Light K29 will go out and the engine can be started.

Extended Glow Period
The extended glow period takes place whenever the engine is started, regardless of whether or not it is preceded by a glow period. This reduces combustion noise, improves idling quality and reduces hydrocarbon emission. The extended glow phase lasts no more than four minutes and is interrupted when the engine speed rises above 2500 rpm.

Glow Plug System Overview