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How to Diagnose Spark Plug Problems

Rahul Thadani
Diagnosing spark plug problems is something that needs to be handled with great caution and care since there are so many different issues that can plague this component of internal combustion engines.
A spark plug is an essential component of any internal combustion engine since this is the part that provides the spark which ignites the fuel-air mixture inside. Their most common use is in automobiles, but there are several other devices and engines that work on this concept and require a dedicated spark plug as well.
Most of these machines cannot work without the ignition that the spark plug provides, and this is what makes it such an important aspect of these engines.
Faulty spark plugs can lead to severe problems in these machines, especially in automobiles. In the worst cases the engine will simply not start, and in milder cases, the engine will suffer from a loss of power and will also experience 'knocking'.
Strange sounds will emanate from the engine when the mixture is being ignited and this could lead to many other problems as well. Hence it becomes very important for the owner of such a machine to recognize these issues as and when they arise, so that the efficiency of the engine does not suffer.

Performing Spark Plug Diagnostics

There are many clear signs that indicate these issues, and someone who is accustomed with the workings of such engines will be able to recognize such signs easily. An experienced mechanic will always look out for these visible indicators whenever someone comes to him with engine trouble.
Moreover, after reading about these signs, even you should be able to diagnose common problems in the future.
The central electrode is the spot that is the hottest during the ignition process, and it is from this spot that the electrons in the form of sparks are emitted. Once an engine has been used for some time, this part wears out and looks extremely pointed in appearance.
This is a clear sign that the spark plug has lived its life and needs to be replaced immediately. In some other cases, this electrode may appear to be burned out completely, or may even look melted. There are several reasons for such a thing to happen but the most common cause is bad quality fuel.
Other possible causes are overheating of the engine, bad timing of the engine or faulty engine valves. It will need to be immediately replaced in such a situation also.
Now if you can see some black deposits on the spark plug that are wet to the touch, then you need to start cleaning it regularly before there is a serious problem. These deposits are nothing but oil (and this condition is known as fouling), and this is a sign that excessive amounts of oil are entering the chamber of the engine.
Whether this is because of a leaky piston or ring is something only a mechanic will be able to tell you. If the deposits are dry and fluffy, then the possible causes for this could be a faulty fuel pump, high idling values of the vehicle, an inappropriate spark plug, a faulty air cleaner, high octane fuel or driving at a low speed for a long time.
Finding the exact cause is the job of a trained professional, but all these problems can be fixed without replacing the plug itself. You will only need to clean it effectively from time to time. Fouling can also occur when there are deposits of carbon of fuel on the plug, and all these are signs that the spark plug needs to be changed as soon as possible.

Signs of Spark Plug Problems

You can only learn the proper way to assess a spark plug once you have a look at it, or get a mechanic to look at it for you. Unfortunately, this is not something that most people do on a regular basis. So here are some signs that you should look out for when you are using your vehicle.
  • The car does not start at all. Alternately, you have to turn the ignition key several times before the car starts.
  • You notice several cases of misfiring in the vehicle, either when the car is moving or when it is idle. Misfiring is a situation where it seems like there is a regular pause between the continuous functioning of the engine.
  • Engine surging is another sign that wires are not working properly. In such a situation the engine starts and stops suddenly and does not move smoothly.
  • If the mileage of your vehicle has seen a sudden drop, then this could also be a direct result of a faulty spark plug.
  • The single biggest indicator such problems is the stalling of the engine from time to time, and a sudden drop in the acceleration from time to time as well.
You cannot learn these things overnight, because there are many problems that arise due to different causes. Someone who has dealt with such issues many times will be able to discern a problem at first glance, but someone who is looking at a spark plug for the first time will have to spend a lot more time to do the same.
As a precautionary measure, you should inspect and clean your spark plug from time to time, and should also a have a mechanic service your engine and its components once every few months.