Signs it’s Time to Replace the Glow Plugs in Your Diesel Engine

Your diesel engine relies on the glow plugs to get it started. The glow plugs work differently from spark plugs. Spark plugs generate a spark to ignite the engine and then continue to generate sparks to keep it running. Glow plugs produce heat inside the combustion chamber to fire up the diesel engine and then shut down until the next time you start the engine. CAR FIX advises that this makes glow plugs last longer than spark plugs. They will go bad eventually, however. Here are signs that yours have.

Difficulty Starting the Engine

The most common sign that your glow plugs are going bad is difficulty starting the diesel engine. The combustion chamber needs to reach a certain temperature in order for the diesel fuel to ignite. If the glow plugs are bad, they may be unable to heat the combustion chamber to 450 degrees Fahrenheit, which is the temperature the chamber must be at in order for ignition.

A Misfiring Engine

Another sign that your combustion chamber is not at the right temperature is if your diesel engine misfires constantly. Misfiring can signal a temperature problem; the engine is too cold. This cold condition can be caused by the glow plugs’ inability to produce heat inside the combustion chamber. As an aside, your engine may also misfire if there is a fuel delivery or compression problem.

A Rough Engine Idle

If the engine is idling roughly, this, too, can be a sign that the glow plugs need to be replaced. The lower the engine temperature gets the rougher the engine will idle. You want a smooth idling engine. When the engine is idling smoothly, this is an indication that the glow plugs are producing enough heat inside the combustion chamber. This also indicates the fuel is being delivered properly.

Poor Fuel Economy

You are seeing a pattern here, but if the engine is running colder than it should be, the diesel fuel will get poor fuel economy. This is because the engine is burning through more of the fuel than it usually would if the engine were at a normal temperature. Even if only one of the glow plugs has gone bad, this can affect the engine’s overall temperature and fuel economy.

White Exhaust Smoke

Finally, your tailpipe may release puffs of white smoke when the engine starts if the combustion chamber is not at 450 degrees Fahrenheit. The white exhaust smoke is definitely a sign of a heating problem in the engine that needs to be addressed as soon as possible.

We can do that here at CAR FIX in Cookeville, Crossville, Knoxville, Maryville, and Oak Ridge, TN. Call the shop closest to you to schedule a glow plug inspection.


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