What are coils in a car engine?

This blog post will answer the question, ‘What are coils in a car engine?’, and cover topics like the functions and structure of an ignition coil, how it helps in the ignition process, and signs of a faulty car ignition coil.

What are coils in a car engine?

Coils or ignition coils in a car engine are responsible for helping the car start. It acts as a voltage amplifier, that amplifies the 12V from the car battery into a much greater voltage to help the spark plugs provide a strong enough spark for igniting the air-fuel mixture.

Functions and structure of an ignition coil

The following are the different functions of a car engine ignition coil:

  • It helps to start the car by amplifying the 12V voltage from the car battery into the required amount for the spark plugs to ignite the air-fuel mixture as 12V on its own is totally inadequate for burning the mixture.
  • The car engine ignition coil helps to increase the voltage between 10,000 and 15,000 volts in some conditions, although the voltage which occurs under normal running conditions is of the order of 4000-5000 volts.
  • Two coils of insulated wire are wound on a laminated soft iron core. The inner coil called the secondary has more turns than the outer primary coil. There are about 20,000 turns on the secondary and 400 turns on the primary coil.
  • If a low voltage current passing through the primary coil is switched off a higher voltage is induced in the secondary coil, the increase being approximately in the same proportion to the number of turns of the two coils.
  • The core and windings are placed in an iron sheath, and the entire assembly of the ignition coil is housed inside a sealed container.
  • A high tension lead cable from the center of the coil carries the supply of the current to the distributor.
  • Two small terminals are situated on either side of the high tension lead cable, one is connected to the contact breaker and marked as CB while the other is connected to the ignition switch and marked as SW.

How does it help in the ignition process?

This is how the ignition coil takes part in the ignition process:

  • Firstly, the ignition switch is turned on and the engine is cranked
  • When the contacts touch, the current flows from the battery through the switch, and the primary winding of the induction coil to the circuit breaker points to complete the circuit through the ground.
  • A condenser connected across the terminals of the contact breaker points prevents the sparking at these points.
  • The rotating cam breaks open the contacts immediately and the breaking of this primary circuit brings about a change in a magnetic field.
  • This leads to the generation of a very high voltage in the range of 8000-1200V across the secondary terminals.
  • Due to the high voltage, the spark jumps across the gap in the spark plug and the air-fuel mixture is ignited in the cylinder.
  • When spark extinction occurs, the circuit becomes open and the current flow is stopped.
  • This causes the magnetic field to collapse, thus inducing a current in the primary winding, which eventually flows into the condenser and helps to charge it.
  • When the voltage in the condenser becomes higher than the primary winding, it discharges back into the primary winding.
  • This results in the collapse of the magnetic field and the rebuilding of the voltage in the secondary winding.
  • This pulsing back and forth and weakening each time continues until the entire energy is dissipated.

Signs of a faulty car ignition coil

These are the following identification signs of a faulty car engine ignition coil.

Car backfires

This is a very common sign of a faulty car ignition coil, and it requires an expensive repair. A car backfiring mainly occurs when the fuel that has not been burnt yet, exits the car through the exhaust pipes.

A car backfiring can be identified when the exhaust pipes of the car emit a thick and dense black-colored smoke, often accompanied by the smell of petrol or diesel.

A decline in fuel economy

One of the most telltale signs of a faulty car engine ignition coil is the sudden drop in the mileage of the car. If left unchecked for long, it will result in poor performance and more fuel consumption.

Misfiring engine

A car engine that suffers from the problem of misfiring, is said to have a faulty ignition coil and is identified by a sputtering noise while starting the car engine. A misfiring car engine also starts jerking or vibrating when at higher speeds or coming to a stop.

Car stalling

A faulty ignition coil can cause the car engine to come to a sudden halt, as it provides an irregular spark for igniting the air-fuel mixture and thus, resulting in improper combustion and less power produced to keep the car in motion.

Rough start to the engine

Sometimes the engine is very difficult to start, or even jerks while starting it. This signifies that the car engine is being turned on without producing any sparks and thus fails to provide enough power for a smooth startup.

The check engine light turns on

The check engine light is visible on the engine tachometer and signifies a primary or secondary coil problem according to the code P0351.

Research has shown the different types of ignition coils available and the ways to test them.

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This blog post addressed the question, ‘What are coils in a car engine?’

We understood the various functions and the structure of a car engine ignition coil and how it helps in the ignition process. Furthermore, the signs of a faulty car ignition coil have also been discussed. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): What are coils in a car engine?

What happens when a coil goes bad on a car?

A faulty car engine ignition coil causes misfires in the car engine, leading to issues during acceleration. This can also result in a car engine stall in extreme cases.

What does a coil do in a car?

The role of an ignition coil is to amplify the voltage from the car battery and transform it into a larger amount, to be able to be used by the spark plugs for igniting the air-fuel mixture with a strong enough spark.

How much does it cost to replace ignition coils?

The estimated cost for replacing the car ignition coils ranges from 160-220$. The labor costs for replacement are covered by 50-60$.