Mercedes Glow Plug Repairs

If you have the Yellow Glow Plug light on your dashboard after the engine has started, then that indicates an issue.

Does your Glow Plug light stay on after startup?

If your Glow light is on after the engine starts, your engine ECU has detected a fault with the glow plugs or control unit.

Mercedes Diesel engine use glow plugs to assist during starting and running in cold weather.

When glow plugs are not functioning correctly, starting performance and exhaust emissions will suffer.

What is a Glow Plug?

A Glow Plug is a heating element that heats the fuel and air within a diesel engine, ensuring quick starting in cold conditions. They are pencil shaped and are installed into the cylinder head of the engine. There is one for each cylinder. There is a control unit which controls when and for how long the glow plugs are heated by electrical current.

In a Mercedes Sprinter or Vito, the Glow Plug light will illuminate on the dashboard before starting, indicating the pre-heating phase. If this Glow light continues to illuminate after starting or whilst driving, it is indicative of a fault with the Glow Plugs.

How does a Glow plug Work?

Glow plugs look like long metal pencils and they are screwed into the engine cylinder head. They have a positive wire connected to the external end, which will cause the tip of the glow plug to glow red hot when powered! Similar to a toaster heating element.

This red hot tip allows the diesel fuel to combust when the engine is cold, improving starting performance and emissions.

Symptoms of faulty Glow Plugs

If your Glow Plugs are faulty, you may notice the following:

Difficult Starting: This is the most common glow plug related symptom and will be most apparent on cold mornings
Engine Misfiring and Smoke: After startup, you may notice a rough running engine or smokey exhaust, which will indicate poor combustion.
Engine Light: Not all models will show an engine light if there is a glow plug fault, However it is common for the V6 models.
Glow Plug Light ON: This is the most common indication of a fault. Remember that the glow plug light should not show after the engine has started.

Repair Methods for Glow Plugs

We recommend the removal of faulty glow plugs as soon as your Mercedes shows the Glow Plug dashboard light after starting.

First, we will diagnose which glow plugs need replacing and whether the glow plug control unit relay will need replacement.

Note that it is often not necessary to replace all 4, 5 or 6 glow plugs at once.

Eurostar Diesels will remove the faulty glow plugs and reinstall new glow plugs with anti-seize lubricant. The repair can be completed in less than a few hours and help your engine run optimally.

In Summary - Glow Plug Light

If your glow plug warning light shows AFTER startup, then you have a fault and you should have the problem diagnosed and repaired. The good news is that you don’t necessarily have to replace all 4, 5 or 6 glow plugs. We’re always happy to chat so give us a call or send us a message!