How to check if your spark plugs have gone bad


If your engine is having issues with starting, that might be from the spark plug. Wonder how to check if your spark plugs have gone bad? You're at the right place. Read on!

If you have a small electric generator, you would have noticed the spark plug at the rear which actually sparks when you pull the ropes that gets the generator to come on. Whenever your generator doesn't come on, the first thing you do is to unscrew the spark plug, clean oil or dirt off it, place it back and try to start again.

This same spark plugs can be found in internal combustion engine of vehicles. Though not the same type found in your small generator, it performs a similar role -, i.e help make the engine start. When you turn the key in your ignition, electrical signals are transmitted from the spark plugs (thanks to the sparks created) to the combustion chamber. Once this signal gets to the chamber, it burns the fuel and air mixture therein and the engine comes alive. When you try to turn on the ignition and the engine doesn't respond, it's probably time to check if your spark plugs have gone bad. But where do you start from? What do you look out for? What signs should you expect? This article by Naijacarnews provides you with all the information you need.

1. Signs of a failing spark plug

The first step to knowing if your spark plugs have gone bad and need to be changed or cleaned is by trying to start the engine. Once it doesn't come on, it's time to check the plugs. Though the car kick starter can also be a culprit but the plugs should be examined. Sometimes, the vehicle might come on but it will misfire. You would probably even hear a pop sound coming from the bonnet. It's likely the spark plugs. A lot of people attribute it to the fuel burning unevenly. No doubt, but in a case where it isn't bad fuel, you'll have to check the plugs.

Aside from misfiring, the acceleration of the vehicle can diminish with time. The spark plugs work hand in hand with a number of components of your vehicle to ensure its smooth running. So if the spark plugs wear out, other parts will be affected. This will eventually cause your car to burn even more fuel. Therefore, if your car shows any of these signs, check the spark plugs.


Bad spark plugs can't ignite the chamber combustion

2. How to troubleshoot the spark plug

2.1. Check for cracks

You should already know what a spark plug looks like. Check for cracks on the cover of the plug and even around the metal area not covered by porcelain. If there's a crack or the metal looks out of place, then the plugs are bad and need to be replaced.

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2.2. Look at the electrode on the side and the tip for deposits

If you find black coloured deposits around the tip or the electrode on the side, it's a sign that a lot of fuel has been running through the spark plugs so they have become soaked. It could also mean that the wiring in the engine has gone bad or your fuel injectors are leaking. In this case, you won't only be trying to sort out the plug issue but also fixing your injector leaks. If not done, the rate at which petrol or gas will be burnt in your engine will be a lot higher. It will also be difficult to clean up the process and you'll have more problems in your hands.


Spark plugs with black-colored deposits around the tip are faulty because they have been fuel-contaminated

2.3. Check for red coating around the insulator

The porcelain insulator is usually white in colour or simply brightly coloured. When you start noticing red coating around it then it's an indication that you have been buying unleaded poor quality fuel. The red coating is an accumulation of additives used in the fuel. So you'll not only need to clean or replace the spark plugs, but also change the filling station you make your purchase from.

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2.4. Measure the spark plug's wire resistance

You need to ascertain the level of resistance of the wires in your spark plugs. This helps you figure out if they are effective. Get a multimeter (preferably a digital one), connect it to the wires. If the resistance goes beyond 10,000 - 15,000 ohms, then the wiring has obviously gone bad. You can't know this bad wiring by merely looking at it, because even a minor cut can increase the resistance.

Video: How To Change & Inspect Spark Plugs5. Pre-firing

We talked about misfiring, let's look at pre-firing. This is when the spark plugs fire sooner than it should. This doesn't give enough time for fuel to be burnt, and the engine can't start. Even if the engine starts, you'll likely be driving a car that can misfire at any time. So change the plugs to avoid any fatalities.

2.5. Observe the colour of the sparks

I bet you never knew that the spark colour has a lot to do with how good or bad the plugs have gotten. Normally, your plug should give out a blue spark. That's a sign that it's still in good shape. Yellow, red or none at all says you need to have the plug replaced. Therefore, with these tips on how to check if your spark plugs have gone bad, you'll be up to speed with happenings in your car to ensure that your engine stays running when you need it to.

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Kennedy Ilediagu


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