How Do Spark Plugs Work: All That You Need to Know

How Do Spark Plugs Work

If you want to know about how do spark plugs work, then you have landed on the right page. Spark plugs are a necessity as you cannot start your car’s engine without spark plugs. They are small insulated plugs with the threaded structure on the end that look like a bolt and are fitted on top of the engine’s cylinder head.

There will be six spark plugs in case of a v6 and four in case of a V4. 

In this article, we are going to talk about spark plugs in detail. Let’s have a look:

How Do Spark Plugs Work?

The basic role of a spark plug is to produce a spark which ignites the fuel in the chamber. It creates combustion in the engine as a result of producing a high voltage which can be between 20,000 to 100,000 volts.  

Let’s know more about how do spark plugs work:

Working Mechanism: Spark plugs are connected to the ignition coil which has the potential to generate a high voltage. A voltage difference is created between the side electrode and the center electrode when electrons start running from the coil.

Important Parts Of A Spark Plug to Know How Do Sparks Plugs Work:

Steel Shell: The outer covering of the spark plug.

Resistance: It controls the current intensity.

2 electrodes: There are two electrodes (central and ground electrode) in a spark plug and both are made up of nickel alloy to withstand corrosion and erosion that takes place when the temperature is very high.

  • Central Electrode: It is insulated using porcelain and its job is to carry high tension current.
  • Ground Electrode: It is attached to the steel shell and becomes grounded when fixed on the engine’s cylinder head.

When the engine is turned on, the high-intensity current runs through the central electrode and ionizes the gas which is present between the electrodes, also called the electrode gap. This turns it into a conductor and as a result, there is a spark.

During the process, when the end of the central electrode and the insulator come into contact with the combustion gases, the insulator may crack because of high thermal stress produced by the high temperature.

Similarly, if the temperature is too low and there’s less load on the insulator, the abnormal surface deposit might appear at the tip of the electrode and prevent it from work properly.

Considering these two problems, spark plugs are divided into two categories.

Hot Spark Plug (Used when combustion temperature is low): They have elongated insulated tips which give them a long heat-rejecting path. This allows them to avoid abnormal surface deposition from taking place on the tip. It can be used on both bikes and cars.

Cold Spark Plugs (Used when combustion temperature is high): The tip on cold spark plugs is short and so is the heat rejection path. This helps them to avoid overheating. They are mostly used in racing cars and trucks.

Now that you know how to do spark plugs work, it is time to know about installing spark plugs and other aspects. Let’s move ahead:

When Do Spark Plugs Fail?

Spark plugs don’t function forever. Commonly, they have a life expectancy of 45,000 kms. After covering this distance, they often begin to show problems and need to be replaced.

Your vehicle will not start if the spark plugs do not work properly, so make sure to replace them when the time arrives.

Mostly, spark plugs fail with time because fuel residue dampens the ignition power.

The other reason for them to fail is when the gap between the two electrodes increases. This is the reason that no spark is generated.

It’s very easy to determine if spark plugs are in good working condition or not. Here are a few factors that will help you check their condition:

Car Won’t Start: This one’s a no-brainer but there are many drivers who think that their vehicles not being able to start might have to do with fuel or a flat battery.

However, battery or fuel is not the only reason why your car won’t start. At times, it is due to spark plugs. It is also often due to faulty spark plugs that drain the battery too quickly.

Engine Misfires: A lot of people think that engine misfires and cars not starting are the same thing. This is nothing but a myth. An engine misfiring is more contagious than an engine not starting at all.

When there’s an issue in the ignition system, spark plugs are typically to blame. There’s a connecting wire that sits at the top of the spark plug. Its role is to pass the voltage and help ignite a spark.

When spark plugs begin to wear out, this wire also gets damaged. Thus, every time one tries to start the engine on, sputtering and stumbling sounds are produced.

Engine misfires are dangerous because they increase exhaust emissions, reduce engine power and cause a drop in fuel economy as well.

Slow Acceleration: Modern vehicles come equipped with multiple sensors that tell the ignition system when to make the spark plugs generate a spark. However, failed spark plugs fail to act accordingly.

If you are pressing your foot down on the acceleration pad and the vehicle doesn’t respond to the action or does not accelerate a the right speed then it is most probably due to faulty spark plugs.

Too Much Of Fuel Consumption: If your vehicle is consuming a lot of fuel then there might be a problem with the spark plugs. In fact, expert mechanics say that a deteriorated spark plug accounts for 30% more fuel combustion because of incompletely fuel combustion.

If you think that you have to fill up the tank much sooner than you used to then it’s a wise choice to check your spark plugs or have it checked by a mechanic.

This happens because the gap between the electrodes in a spark plug either shrinks or extends and makes it hard for the spark plugs to create sparks.

Engine Working Efficiently: If your vehicle begins to start and stop automatically and also jerk randomly then it might be due to poor spark plugs. Moreover, the car slowing down is also a sign of something being wrong with spark plugs.

This happens when engine combustion sucks up more air than it should and makes the engine run inefficiently. It is also referred to as engine hesitation and if your vehicle is doing the same, it’s better to have the spark plugs examined or do it yourself.

Engine Idles Roughly: This happens when your engine is operational but the vehicle is stationary. In this situation, your vehicle produces a low RPM (1000 rpm),

If you are noticing a harsh and sharp sound when starting the engine, then your car’s spark plugs might be damaged. Along with the jittery sounds made by the engine, you will feel a constant vibration, too.

This shouldn’t be neglected because it can largely affect the engine’s performance. So, if you feel that the engine sound is not smooth and constant then have the spark plugs checked.

Now that we know how do spark plugs work and when spark plugs fail, let’s get to know about how to replace them.

How To Replace Spark Plugs?

If you want your engine to run perfectly and for longer then it’s vital to make sure that the spark plugs work perfectly. Changing spark plugs at the right time improves the mileage and performance of the engine.

We know that the gap between two electrodes in a spark plug can get damaged as the metal begins to erode with time. Continuous erosion keeps on increasing the gap to the point where no spark is initiated by it and the engine does not turn on. Hence things like poor mileage, slow acceleration, harsh engine sounds, jerks, vibrations, and misfires accompany.

If you want to keep your engine safe and your car in working order then it’s vital to change the spark plugs when they fail.

Here’s how to do it:

Step 1 – Locate Spark Plugs, Get Your Tools Ready And Make Sure The Engine is Cool

Open the hood and look around the rubbery wires for spark plugs. There might be four of them if it’s a v4 engine or six of them if it’s a v6. Clean off the dirt from the top and even blast air if possible. This will help you get a good look at all the components.

Locating Spark Plugs: Look for 4-8 wires that run to different points on the engine compartment. These wires end with a plug cover and have spark plugs attached inside of them.

If it’s a V4 engine, the spark plugs will be located on the top of the engine in a row. In the case of a v6 engine, spark plugs will typically be on the top side of the engine, separated evenly.

Note that not all engines have spark plugs visible as you open the hood. There might be a cover on top of them which you will have to remove to get access to the plugs.

Tools Required:

Let The Engine To Cool Off: Don’t try to take the plugs out or insert new ones while the engine is hot.

Step 2 – Remove The Ignition Coil

The next step involves removing the ignition coil attached at the top of the spark plug.

You will have to twist it about a quarter so that the o-ring seal breaks loose.

Once it does, grab it and pull straight up and out and the coil will be removed.

This type of ignition coil is found in engines that have a COP ignition system, if your car doesn’t have this system then you might need a wire puller to detach the coil.

Use a spark plug wire puller and grab the boot with it. Apply force to pull out the cord.

Step 3 – Unscrew The Plug

Grab a swivel spark plug socket and an extension to unscrew the plug. The trick is to use a suitably sized spark plug socket and an extension so that you can reach to the plug.

With the plug socket, rotate the plug counterclockwise to open it. If it’s too hard, apply some force and it will begin to rotate.

Step 4 – Use a Gap Gauge to Gap The Plugs

Avoid using a disc-style gauge because they can make bends on the center of an electrode and even damage it. Use a wire style gap gauge instead.

Pick the right sized wire gap gauge and slide it between the side and center of the electrode. Now adjust the gap by pushing or pulling the gap gauge. Always check if the gap is perfectly adjusted or not.

Now choose any anti-seize compound and dab it on the threads of the plug. Once done, hand thread the plug on top of the cylinder.

Step 5 – Installing The New Plug

Grab a torque wrench and apply torque on the plug to settle it down. Too much torque is harmful to the plug because it will force the plug to exit out of the cylinder head along with the thread.

Dabbing a small amount of anti-seize compounds can reduce torque by 10% making the job easier.

Place the plug inside and begin to tighten it.

Use the torque wrench and apply force to screw it in.

Step 6 – Lubing The Boot

Once the plug is settled in, apply a dollop of dielectric grease at the end of the tube and spread it at all corners of the boot with the help of a tool.

This will make the spark plug removal easier and smooth in case you need to do it in the future. Also, it reduces engine misfires.

Bring the ignition coil back to its place, which is on top of the plug, and attach it back to it.

And you’re done replacing the spark plug.

How To Replace Spark Plugs? (The Ultimate Guide)

Final Words

Now that you know how to do spark plugs work, we are sure you will have no problem in understanding their importance.

If they have failed to work then following the above mentioned stepwise approach will help you remove them and install new ones easily so that they work without any issue. However, visiting a professional is a better option to ensure that spark plugs work well as they know more about how to do spark plugs work than you do.

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