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Mercedes can sometimes develop problems with their glow plug, otherwise known as glow plug timer relay. Glow plugs are an important part of your Mercedes engine, since they provide the heat and power needed in order to start the car.
There are a few common indicators to look out for that may mean your glow plug has failed, including the check engine light or glow plug warning light, as well as problems starting the engine or problems with the engine misfiring.
You may wonder what a glow plug does. Depending on what type of engine your car has, the ignition processes differ. Instead of spark plugs, a Mercedes diesel engine relies on glow plugs to start up. Glow plugs provide power generated by high temperatures and high levels of pressure to start the engine via engine cylinders, instead of the more common spark plugs in other vehicles.
Because of such high levels of heat, the longer glow plugs stay activated the more damage they can incur over time. On the other hand, if they don’t stay powered long enough, then they may not provide enough heat for the combustion process. This is where glow plug timers come in. A timer with a relay tells the glow plug to activate or deactivate at certain times in the process. If your Mercedes relay timer is faulty, then you may experience issues operating your vehicle.
Common Glow Plug Failure Indications
Below are a few common indications your Mercedes may display that could mean your glow plug has failed.
- Check engine or glow plug warning light: Either of these lights may come on when your Mercedes ECU finds an issue with the engine operative systems. Usually a code is attached, which helps your mechanic find the source of the issue.
- Problems starting the engine: Your engine performance is most at risk when it comes to glow plug or timer issues. If either of these are not working like they should, your engine will have a difficult time starting, if it even starts at all.
- Engine misfires or has reduced power: If the glow plugs aren’t functioning properly, you may notice a decrease in engine performance as they degenerate. This can be gradual or sometimes happen overnight.
- White or black exhaust smoke: Failed glow plugs can affect the diesel combustion process, which then produces black or white smoke. This can be a symptom of many other vehicle issues so it’s important to see a licensed mechanic to have your engine diagnosed.
- Rough idling: If your glow plugs have burned out or become carbon fouled or otherwise damaged, the engine will become more and more difficult to start, especially as temperatures get colder. Your Mercedes will idle roughly and may produce white smoke from the tailpipe once it does start up.
- Decreased fuel efficiency: Glow plugs provide additional heat in the combustion chamber, especially for those who have vehicles in colder climates where blended fuel may be the norm. If the needed temperature is not reached due to issues with your glow plugs, your engine will have to work even harder to meet the demands of the road, leading to negatively-impacted fuel efficiency.
European Motor Cars for Your Glow Plugs
If you experience any of the above symptoms, the best thing you can do is take your Mercedes to a trusted mechanic to have the engine properly diagnosed. 
From there, your mechanic will be able to test the glow plugs and glow plug relay timer to find out if they need to be replaced.
European Motor Cars can diagnose your Mercedes and get you back on the road in no time. We are experts when it comes to Mercedes repair, maintenance, and diagnosis with over 30 years of experience to prove it. Our highly-skilled technicians use state-of-the-art machinery, tools, & technology to provide you with the best possible service.
European Motor Cars has serviced Mercedes drivers in Summerlin, Spring Valley, and Las Vegas, NV, and strives to provide a level of excellence and professionalism that is unmatched. Call us or bring your vehicle in today and get it fixed right the first time.
