What is a Spark Plug? | Symptoms of a bad Spark Plug

Engine is one of the most important parts of the vehicle. It contains multiple parts and the spark plug is one of them. The spark plug is usually used in petrol engine. For the efficient working of the engine, your spark plug must work efficiently. As the spark plug goes bad, it produces different signs. This article explains the symptoms of the bad spark plug.

What is Spark Plug?

A spark plug is a mechanical device that generates an electric spark to ignite the compressed fuel-air mixture inside the combustion chamber. It gets power by the ignition system.

The spark plugs are most commonly used for the petrol engines. However, in the diesel engines, combustion of the air-fuel mixture occurs due to high compression of the air. Therefore, diesel engines don’t require spark plugs to ignite the air-fuel mixture.

Construction of Spark Plug

Spark plugs have a threaded metal shell. Ceramic insulator is used to electrically insulate the shell from the central electrode. This central electrode usually contains a resistor. It connects to the output terminals of the magneto or ignition coil through a highly insulated wire.

The metal shell of the spark plug is electrically grounded. It also connects to the cylinder head of the engine. The center electrode protrudes into the combustor through a porcelain insulator.

Signs of Bad Spark Plugs

1) Reduced gas mileage

A quick reduction in the gas mileage is one of the main signs of the dirty or bad spark plug.  If your spark plug is clogged or damaged, it will not work efficiently which can negatively affect fuel economy.

2) Lack of acceleration

The damaged spark plugs highly affect the acceleration ability of the engine. As the spark plugs are damaged, your engine doesn’t run the vehicle according to your requirements.

Dirty spark plugs don’t have ability to catch spark effectively and can slow the engine, especially when changing gears.

3) Hard starts

If the car does not start after attempting multiple times, your car spark plugs may be defective. In order to ignite air-fuel mixture of all cylinders in time, the engine requires a powerful ignition spark. If one or more plugs are not working efficiently, your vehicle engine will not get the spark according to the requirements. This can cause one or more cylinders to malfunction and make it difficult to start the engine.

If your car is not starting, then check the spark plugs. If the plug is damaged, replace it with new one.

4) Engine Won’t Start

If your car’s engine won’t start, it is one of the main symptoms of a bad spark plug. The car engine won’t start due to some other possible causes such as bad alternator, a bad ignition, or dead battery.

If the battery check reveals that it is not fully charged while the battery terminals or cables are not corroded, the next best idea is to inspect the spark plugs (the alternator and ignition are difficult to diagnose on their own). You must properly maintain the spark plug and replace it on time.

5) Engine Knocking

As the spark plug goes bad, you may hear knocking noise from the engine. This is a very serious problem that may cause the complete failure of the engine. The damaged spark plugs may also damage the important engine parts such as pistons, valves, compression rings, piston heads, and the engine cylinder.

6) Black Exhaust Smoke

The bad spark plugs may lead to higher emission of the exhaust gases and black exhaust smoke. As you notice this symptom, you must immediately contact to a specialist to diagnose the problem.  The engine may emit black smoke due to engine oil entry in the combustion chamber or low coolant.

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