Mercedes SUV Glow Plug Indicator Light

glow plug image

One of the most frequent indicator lights to be illuminated on Mercedes SUVs is the glow plug warning light (symbol of a heating element coil). Glow plugs are heating devices, located in the combustion chamber, whose purpose is to preheat, and help warm up your engine’s cylinders so that diesel combustion can occur more easily. When they are not functioning properly, they can usually cause problems with the drivability of the vehicle.

Why The Glow Plug Indicator is Activated

The Glow Plug indicator will either come on and stay on or flash on and off when a fault is detected by the engine management unit (EMU). When the Glow Plug Light comes on, the ECU stores information about the condition that has caused it to come on.  At Norlang Auto, our qualified and experienced technicians have the latest factory diagnostic equipment to retrieve this information, and then make an accurate diagnosis of the problem.

It’s inevitable that glow plugs will wear out over the course of time and will need to be replaced.  However, our technicians have noticed that if you replace the glow plug module before replacing the glow plugs, in the 5 cylinder engine, you will most likely damage the new module.  In addition, we’ve noticed that for the 6 cylinder engine, the module rarely fails but the glow plugs tend to break off in the cylinder head.

Symptoms of Failing Glow Plugs

Normally, bad or failing glow plugs will produce a number of symptoms that will alert you that your Mercedes SUV is experiencing problems. You are advised to take notice of these symptoms and visit professional technicians, like those at Norlang Auto, to find out if your glow plugs need to be replaced before serious and costly damage is done to your engine.

Engine Misfire

One of the most likely symptoms of failed glow plugs is your engine misfiring since they will not provide the necessary heat to help in diesel combustion.  Naturally, misfires may also result in loss of power or acceleration and in a drop in fuel efficiency.

Hard Start

An additional symptom is hard starting.  Due to the fact that diesel engines do not use a spark to ignite the fuel mixture but instead rely on cylinder pressure to accomplish this, if your glow plugs fail then the engine will have to overcome additional pressure in order to ignite the mixture, which may result in hard starting.

Black Smoke

Finally, if you notice black smoke from your exhaust it could be the result of failed glow plugs since they can affect the diesel combustion process and cause the engine to produce the black smoke.  However, black smoke can be the result of a number of issues that is why it’s necessary to have professionals diagnose the problem.

If you have any questions regarding this issue, please feel free to contact or visit us, so we can address your concerns.

Call us today or contact us online to schedule an appointment and experience what we can do for you!