Automotive Maintenance And Detailing


Automotive Maintenance And Detailing

What is the purpose of a spark plug in car?


Spark plug in a car is essential parts of the engine to spin and deliver power to the wheels, allowing the vehicles to move, taking you places. 


The diesel vehicles do not install the spark plug.


The operation of the spark plug is directly related to the ignition system in the combustion chamber located just above the piston. As a result of the ignition by the spark plug, the pistons will move up and down. Then rotate the crankshaft with the connecting rod.  That keeps the engine running and energizing.


You have to understand the function of spark plugs and their service life. Spark plugs will expire after a while, and you need to replace them when they start to break down.


Spark plug replacement can range from easy to difficult that you can do yourself or requiring special tools by a skilled technician.

Parts of a spark plug


Spark plugs are in metal and white ceramic, with terminals at the head and tail. It has the following components.

  1. Terminal Nut. It is used for spark plug wires to receive high voltage from ignition coils or distributor
  2. Insulator is a white part made of ceramic, has a corrugated shape Is responsible for separating the ground from the central pole
  3. Body and bolts. This part is made of metal and has a hexagon head to for tightened with a wrench.
  4. This washer is used as a seal to prevent the fuel mixture from leaking out through the spark plug thread.
  5. Central electrode It is made of various metals ranging from ordinary metal, titanium, iridium. This central electrode passes current through the earth electrode. The sparks that arise between the two terminals ignite the fuel.

How do spark plugs in a car make the engine start?

The car spark plugs are shaped white rods with high voltage electrodes to ignite the air and oil mixture in the combustion chamber above the piston. Each piston has one spark plug installed.

In modern cars, the spark plug receives power from the ignition coil attached to the spark plug. The ignition coil is responsible for converting 12 or 24 volts from your car battery to tens of thousands of volts through the spark plug in the combustion chamber.

When you start the engine, several functions will be working simultaneously to cause the engine to start.

A high-pressure fuel pump delivers fuel from the tank along the fuel line. The air duct in front of the car sends air into the intake pipe and mixes it with oil in the intake chamber to prepare it to flow into the combustion chamber. Above the combustion chamber, there is a high-pressure fuel nozzle, spraying oil mist into the inside of the cylinder.

At the same time, the starter motor rotates the engine so that the piston absorbs and compresses the air mixed with the fuel to be dense and heat. The spark from a spark plug causes the fuel to quickly burnt and exploded above the piston. The piston moves down, causing the power to rotate the crankshaft. Then the transmission is powered and rotates at the appropriate ratio in each gear to turn the wheels of the car, resulting in the speed of the car’s movement.

You will see that if your car doesn’t have spark plugs or it is broke, the engine will not be able to start. The spark plug itself, without the ignition coil, delivers high voltage cannot ignite the fuel mixture either.

The spark plug (S) ignite fuel in the combustion chamber

Car spark plug type

Hot and cold spark plugs have a different length of the insulator

There are two main types of spark plugs:

  1. Hot spark plug, this type of spark plug has a relatively high temperature. As you can see, the length of insulator is quite long.

               Hot spark plugs are suitable for general car engines that need to maintain a high temperature in the combustion chamber for good ignition of fuel.

  1. Cold spark plug.  A cold spark plug has a shortter insulator then the hot .  It is a spark plug used in high-performance engines such as sports cars, racing cars. The vehicles in this category have powertrains that have a high rev, causing a large amount of heat to accumulate. Therefore, using a well-ventilated cold spark plug will not cause a faulty ignition problem.

Most of these spark plugs have a small length to dissipate heat quickly.

In case if your car is a general-purpose vehicle such as an economy car, a sedan, a pickup truck. The hot spark plug is the right spark plug for the engine.

However, you should check your owner’s manual that specifies the spark plugs or not. Because besides the correct spark plug type and engine specification, you also need to find out how much the manufacturer specifies to set the electrode spacing. The right gap has a direct effect on ignition performance.

Symptoms of broken spark plugs in the car

Broken spark plugs can affect a car with several symptoms, which you can feel even without knowledge of the engine. The main symptoms of a broken spark plug include the following.

  1. The smell of burning fuel. You will smell the pungent smell of car fuel from the tailpipe. It’s a symptom of a spark plug not being able to ignite the fuel mixture in one or more of the cylinders. The unburnt fuel therefore released with the exhaust.
  1. Has a high consumption rate. The failure of some cylinders to ignite the oxygen sensor, which detects the amount of oxygen in the exhaust, finds a malfunction of the ignition system. The ECU controls the ignition to malfunction the fuel-air mixture. Most of the time, a rich fuel mixture results in higher fuel consumption than usual. For example, a tank of gas used to take you 700. Kilometers but reduced to only 500 kilometers
  1. The engine vibrates. It is the reason for unperfect ignition. Some cylinders do not ignite. For example, the engine runs only three from four cylinders. The car engine that does not run on all cylinders like this will cause uneven running and shaking. You will feel the malfunction immediately if you use the car every day.
  1. Warning light is ON. An orange engine warning light may light up, indicating that there is a problem with your vehicle. You can never know which car part is broke. You need a tool called OBDII scanner to scan errors from your car’s computer system. The most common mistake associated with this is a misfire. You can take the vehicle to a mechanic to scanning and fix it as it is the standard equipment most mechanics use.

When should you change the spark plug ?.

Spark plugs have a service life according to the quality of the materials used. Typical cars with hot spark plugs often replaced every 50,000 kilometers or 30,000 miles. That is because it is the making of ceramics and ordinary metal grades.

Cars with higher grade metal spark plugs such as titanium and iridium will last longer. It usually changes at distances of one 100,000 kilometers or 60,000 miles or more. Sure, these types of spark plugs are more expensive than the ordinary ones, but they’ll save you twice the cost of replacing a conventional grade spark plug.

However, the problem of spark plugs may not always be the cause of a broken spark plug.  But it could be caused by a broken ignition coil. The ignition coil has a service life of about 100,000 kilometers or more. It will start to fail one by one when the time comes. The symptom is no power to the spark plug, or it is intermittent.

The ignition coil & spark plug in modern car.

So you can check whether the spark plug or ignition coil is broke by swapping the spark plug or ignition coil to work with another piston.

There is also a way to check whether the coil is still good or not by inserting a screwdriver rod to the electrode of the ignition coil. Starting the engine and place the metal tip of the screwdriver against an engine metal part at about a centimeter of distance. A good ignition coil will have sparks running between the metal tip of the screwdriver and the engine metal.  Caution: don’t touch the metal or you could die from high voltage.

If your vehicle has a pre-2000s vehicle that comes with the coil and a distributor and spark plug wires, the problem could be caused by a broken coil and distributor or leaking spark plug wire. You can test it with a screwdriver as we have described for both the distributor and spark plug wires by chasing the wires one by one.

Coil & distributor of early 2000s' vehicles

How to replace spark plug ?.

You can replace the spark plug yourself if the tools are ready. The necessary tool is a spark plug block wrench. Spark plugs come in hexagonal sizes, from 11 mm. And up. You will need to know their dimensions first to purchase the exact size wrench.

Modern cars have ignition coils installed directly on the spark plug terminals.

  1. You need to locate the said coil and unplug the power.
  2. Use air to blow away dirt that may be stuck on the spark plug hole.
  3. Tighten the coil fixing bolt. Pull the coil out of the spark plug.
  4. Use a wrench to remove the spark plug from the cylinder. You may find it difficult to screw off. Therefore, the lubricant should be injected underneath the spark plug nut and then slowly exert a tightening force. Be careful not to break or split the spark plugs, as this will result in you having to remove the cylinder head block for the spark plug removal.
  5. Check the spark plug gap to meet the vehicle manufacturer’s standards and tighten the spark plugs.
  6. Plug the ignition coil into the spark plug terminal.
  7. Secure the coil locking nut and plug the coil back in.

Start the engine to check if the engine runs smoothly.

Removing car engine coils and spark plugs

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