All about Spark Plugs


First off, let us get the boring bit of information out of the way. A spark plug is a component that delivers electric current from the ignition system to the combustion chamber in a petrol engine. Now that we have that bit out of our way, let us get to the stuff that matters. Almost all of us have been hearing the term spark plugs since our childhood as they have been a mainstay of petrol engines. Many of us have also seen them, held them and wondered at their size and functionality. But they do not stop working once your car cranks up. They keep working tirelessly, lighting up air-fuel mixture in the combustion chamber and also clearing the chambers of harmful deposits that can otherwise cause your car’s engine to seize.

To help conduct electric spark better and efficiently, copper is used as the central electrode. Earlier, nickel alloys were used but they could not meet the demands posed by around-town driving and high-speed driving both at the same time. Today, you can find spark plugs using Iridium, Yttrium, Tungsten (yes the same as used in conventional light bulbs) or Palladium (the mention in Iron Man movies was not of some fictitious substance but this). Later, Platinum, Silver and Gold also saw usage as central electrode in spark plugs. There was a time when Polonium (the same thing which has been used to poison a lot many folks) was also used as a central electrode. However, you would find Iridium Spark Plugs or Platinum Spark plugs more easily than the rest.

Now that we know a bit about spark plugs, let us know what happens to them when they age.

Okay, they age. But tell me how?

As we have already mentioned, spark plugs are the reason why petrol engines fire up and keep running. This puts them under immense pressure and by the time they would need replacement, they would have already helped you clock a lot of distance on the odometer (when we say quite a lot, we mean above 40,000 at least). But since they sustain themselves under a lot of pressure, they eventually give way to new units. Deposits start forming on spark plugs too as they come in contact with air-fuel mixture. This leads to pre-ignition of the air-fuel mix, making your car feel jerky whenever you ask it for more power.

The second thing that spark plugs encounter over time is expanding gap. Spark plugs are not always peeking inside the combustion chambers. They move inside the chamber exactly when needed to ignite the air-fuel mix to provide the right amount of combustion when needed. As they have to sustain extreme temperatures, wear and tear, and deposits (the same ones we talked about in previous para), the distance they have to travel increases. If this gap becomes too wide, your engine will witness erratic or ineffective combustion, leading to loss of power and fuel economy.

What solutions do I have for the situations mentioned above?

Spark plugs are the kind of components that are meant to do a specific job. For that, they are exiled to a life of isolation inside the engine. Since they survive extreme temperatures and driving conditions, by the time they start showing their age, the only thing you can do to put them out of their misery is get them replaced. However, if it is just deposits over them that are causing them to malfunction, you can get them cleaned and they will be back to work.

What signs indicate that I need to replace the spark plugs?

There are quite a few signs that will help you realise that it is time to get new spark plugs for your car’s engine. Among the obvious tell-tale signs are Pinging/Rattling/Knock-like noises. These noises are caused by misfiring spark plugs. Also, these noises are not the occasional kind. They keep coming as long as your car keeps running. This is because your car’s pistons are working continuously to deliver the power you ask them to. Misfiring spark plugs cause the air-fuel mixture to burn irregularly, leading to all the pinging/rattling/knock-like sounds that you would get to hear.

Another sign of failing spark plugs is a jerky firing up your car. As spark plugs start misfiring due to the issues we mentioned earlier, the pistons start misfiring from the get-go. When that happens, even the firing-up process becomes jerky and hard.

Apart from the above-mentioned symptoms, aged spark plugs also lead your vehicle to start guzzling on fuel to dole out the same amount of power as it used to earlier, leading to poor fuel economy. This is what necessitates the replacement of aged spark plugs at the earliest.

What are the benefits of replacing the spark plugs?

Apart from the obvious gains in power and fuel economy, spark plugs save your engine from damage by making the pistons fire at set intervals. Also, the immediate change you will witness is the way your car starts cleanly and smoothly. Lastly, efficient combustion in the combustion chamber will cause your car’s engine to generate less harmful emissions. So, not only do you get to enjoy a great drive, your carbon footprint also comes down, all due to replacement of aged spark plugs with new ones.

How often do I need to get them changed? How complicated is the task?

Like we mentioned earlier, spark plugs help you cover quite a distance before needing replacement. For the copper ones, the change happens close to 50,000 km while the Iridium and Platinum ones can go even longer before needing a replacement. So, you can take it easy when it comes to spark plug replacement for you would be doing your car a great service in return for the service it gave you.

As far as the complications are concerned, most cars on Indian roads pose little challenge for those intending to get their car’s spark plugs changed. However, on high-end cars, the process may be complicated as those engines differ in the way there are made as compared to the mass-market cars. Whichever may be the case, this is one fix you should not scratch your head over as it is as rare a fix as it can possibly be.