When To Replace Truck Glow Plugs

Diesel truck engines depend on compression to initiate combustion within the cylinders. Heating is necessary within the cylinder for the compression to cause ignition. The sources of heat within the combustion chamber are the glow plugs. Shared in this guide is how and when you need to replace truck glow plugs.

What Are Glow Plugs?

The ignition system of a diesel engine has various parts, and the glow plugs are some of the essential heating elements of the ignition system. The glow plugs are inside each cylinder and rely on the battery to power up. The heat generated by the glow plug ignites the diesel fuel when the engine starts.

The Right Time to Replace the Glow Plugs

Understanding some signs of failing glow plugs is essential to avoid more damage to the ignition system.

If your glow plug is not functional, the combustion chamber will not receive the heat necessary to initiate the combustion. There are some common signs of failing glow plugs.

Emission of A lot of Smoke

When your glow plugs are faulty, your truck will emit a lot of smoke. If the smoke is white, there is no adequate heat to burn up the fuel in the combustion chamber. The unburnt fuel will come out of the engine as white smoke producing a rich fuel smell.

When the glow plug is faulty, it will tamper with the sensitive diesel combustion, producing black smoke.

Increased Fuel Consumption

Usually, the diesel consumption depends on the temperatures, but sometimes the glow plug plays a role. Diesel is blended with additives to lower its freezing point when it is freezing. The blended diesel will need more heat to burn, and the glow plug supplies heat for the combustion to take place. 

If the glow plug is faulty, it will not provide the additional heat to initiate combustion. And this weakens the engine’s performance as fuel consumption increases.

Engine Misfire

A high rate of compression is necessary for combustion to take place in the diesel engine. Fuel and air must be injected correctly and in the required quantity. When the glow plug is faulty, it might not be able to heat up the fuel and air mixture in the combustion chamber, and your engine will misfire.

Hard Starting

Another common indicator of a faulty glow plug is hard starting. When it is cold and the glow plug is faulty, the combustion chamber may fail to reach the right temperature to initiate the combustion, making it hard to start the engine. If you experience such, and the battery and fuel are okay, consider checking the glow plug.

Rough Idling

If any glow plugs are faulty, your truck will experience rough idling and produce white smoke. When you realize there is a problem with how your truck is idling, consider checking the condition of the glow plugs.


The glow plugs are vital in initiating the combustion within the diesel engine. It is an integral part that will likely halt the way your truck functions if faulty. If your truck shows any of the above signs, attribute them to faulty or bad glow plugs. Consider taking your truck for a mechanical check-up and replacing them if necessary.

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