How Spark Plug Work In Trucks

A spark plug is one of the electrical components of the petrol engine. And it sits on top of each of the engine cylinders. In the cylinder, the combustion of fuel and air occurs. For the combustion to occur, the mixture of fuel and air requires ignition, and the spark plug generates the spark.

The combustion engines depend on the spark plug to initiate combustion within the cylinders. The spark plug receives electric power from the battery. This power generates sparks in the cylinder, which initiates combustion.

Functions of a Spark Plug

Here are the two primary functions of a spark plug.


The spark plugs depend on the electricity from the battery to cause an ignition. The energy is transmitted through the spark plug to the firing end within the cylinders. When the voltage is high enough, it will spark the mixture of gasoline and air in the cylinder. The gasoline and air mixture will burn upon ignition, making the piston move up and down. The up-and-down movement of the piston rotates the crankshaft.

Heat Dispersal

During combustion, the temperature goes up within the cylinders. The spark plug plays a role in dispersing the high temperatures. Spark plugs never generate heat, but they only remove the generated heat. The spark plug’s firing end must have a low temperature to prevent a pre-ignition, but this temperature should also be relatively high to prevent fouling.

The spark plug pulls the unnecessary heat from the combustion chamber to the engine’s cooling system. Spark plugs have a hitting range that is their ability to perform an effective heat dispersal from the tip.

How Spark Plug Works

The spark plug directly connects to the ignition coil, which supplies it with high voltage. The electrode flow in the coil initiates a voltage difference between the electrode’s side and center. In the cylinder, no current can flow due to the existence of the mixture of gasoline and air that acts as an insulator. But as the voltage keeps rising, the structure of the gases between the electrodes starts to change.

When the strength of the voltage exceeds the dielectric strength of the gases, they become ionized. An ionized gas conducts electricity and, therefore, allows the electrons to flow through the gap that is the gasoline and air mixture. Spark plugs usually require a high voltage of more than 20,000 volts to initiate combustion.

The fluctuation of the current of the electrons in the combustion chamber leads to an increase in the temperature of the spark channel. Due to the extreme heat, the ionized gases rise very fast, initiating small explosions like thunder and lightning.

The reaction of gases at the end of the spark plug leads to the generation of a small ball. The size of the fireball varies. A small fireball makes the engine run as if the ignition timing is retarded. On the other hand, a big fireball makes the engine run as if the timing is advanced.


The spark plug is an integral component of a gasoline engine. As a truck owner, it is necessary to know how it works per this guide. It is one of the engine components that require regular maintenance. Knowing its location and how to replace it is an added advantage.

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.