Glow plugs are an essential element in diesel engines, especially important during cold starts. Regular inspection, maintenance and replacement of damaged glow plugs are crucial to reliable engine starting and operation. If you experience engine starting problems, glow plug diagnosis should be one of your first steps.

How do glow plugs work?

Glow plugs are electric heaters located in the combustion chambers of each cylinder of a diesel engine. When the ignition is turned on, the glow plugs are powered by the battery, which causes their heating elements to heat up quickly. They heat the air in the combustion chamber to a high temperature (even above 1000°C), which facilitates the ignition of the fuel-air mixture when starting the engine. Once the engine is started, the glow plugs may continue to operate for a short period of time to ensure stable engine operation, especially in cold conditions.

Common glow plug problems:

• Difficulty starting the engine: Damaged glow plugs can cause engine starting problems, especially in low temperatures. The engine may require extended cranking to start.
• Engine Runs Rough After Starting: If one or more glow plugs are not functioning properly, the engine may run rough and produce excessive smoke for the first few seconds after starting.
• Glow plugs do not heat: This may be due to damage to the plugs, electrical wires, relay or glow plug controller.

Glow plug maintenance and diagnostics:

• Regular inspection: Check the glow plugs regularly for wear and damage. Check the electrical connections to make sure the wires are secure and free from damage.
• Testing Glow Plugs: Use a multimeter to check the resistance of each glow plug. The resistance should be in accordance with the manufacturer's technical data; too high or too low resistance may indicate a damaged spark plug. You can also check the voltage at the glow plugs during cranking to make sure they are receiving the proper voltage from the relay.
• Replacing glow plugs: Glow plugs are wearing parts and should be replaced in accordance with the manufacturer's recommendations, usually every few years or tens of thousands of kilometers. When replacing glow plugs, make sure that the new plug is suitable for your specific engine model.