Glow plugs are necessary because diesel engines produce the heat necessary to ignite the air-fuel mixture by compressing the air in the cylinder and combustion chamber. In cold weather, and when the cylinder block, engine oil and coolant are cold, the heat produced by the first revolutions of the crankshaft is absorbed by the surrounding components, preventing the air-fuel mixture from igniting. Glow plugs are activated before the engine cranks, warming up the combustion chamber, and remain activated for some time to ensure the ignition of the first charges of the air-fuel mixture. Once the engine starts, there is no need for glow plugs, although in some engines the glow plugs continue to operate for 5-10 seconds after starting to ensure smooth and efficient operation, and sometimes also to regulate the amount of harmful emissions, since the completeness of combustion of the air-fuel mixture in a cold engine is significantly impaired. During this period, the power supplied to the glow plugs is significantly reduced to prevent pre-ignition.
The glow plugs are controlled by the pre-heating system control unit. Temperature and power consumption are controlled by the engine management system, providing a wide heating range in accordance with the required mode. Power is supplied individually to each glow plug. This ensures optimum heating time for the glow plugs, minimizing the waiting time for the engine to start and maximizing the service life of the plugs. If a malfunction occurs in the pre-heating system, the corresponding fault code will be transmitted to the driver information center.
A normally functioning system works as follows:
- Turn on the ignition with the engine off and at room temperature.
- The glow plugs are turned on and heated continuously for two seconds, then in pulses for another two seconds.
- The glow plug indicator lamp comes on for one second when the engine is cold started.
- The pre-heating system indicator lamp should not light when starting a warm engine.
- If the engine crankshaft is rotated by the starter during or after the above, the glow plugs should turn on and off after the ignition returns from the starting mode, regardless of whether the engine has started or not. Starting the engine does not cancel the glow plug cycle.
Original source on the website opelbook.ru
The initialization time of the glow plugs varies depending on the system voltage and temperature. Lower temperatures make the glow plug glow longer.
The engine control unit ensures that the glow plugs operate after a cold start of the engine. This post-start function is initiated after the ignition switch is returned to the "Run" position (engine operation) from the "Start" position (crankshaft rotation by starter). This function helps to eliminate white smoke from the exhaust pipe and/or unstable engine idling.
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