Working of car ignition system


You might have encountered a situation when you were ready to go for an urgent work but your car fails to start. No matter how many times you turn the keys, you are unable to hear that vroom sound you love to hear from your car. Upon calling a mechanic, you come to know that there is some fault in the ignition system of the car. The obvious question that arises in mind is how ignition system works? And what are those unfamiliar components used in ignition system? Why it’s not simple to burn the fuel inside engine? In this article we are going to cover the basic details of ignition system’s working.

All right let’s start with the basic introduction and detailed working of car ignition system. Well ignition system is the combination of

  • Battery
  • Induction coil
  • distributor
  • high voltage conduction coil winding coil
  • spark plugs etc

These collectively work to create a spark inside the combustion chamber.

It’s quite important to know at this point that a car battery produces 6 to 12 volts but a voltage of around 40,000 to 100,000 is required to generate a spark from spark plug. So how the spark plug manages to produce that much voltage?  The principle behind this phenomenon is that when electricity flows in a coil of wire, a magnetic field is produced and energy is stored. When the current stops, magnetic field breaks down resulting into a voltage spike in the coil of wire within the field lines of force. This   process takes place in the induction coil. Let’s get into more details for better understanding.

Induction Coil

Induction coil consists of

  • Soft iron core which concentrates the magnetic field.
  • Thick wire coil for primary winding.
  • Thin wire coil for secondary winding.

The primary coils(primary winding) has  few 100 turns around the soft iron core acting as low voltage part which is connected to the battery while secondary coil(secondary winding) can have several thousand turns perhaps up to fifteen hundred meters in all, acting as high voltage part. It’s kind of a mini transformer.

Working of induction coil

When the ignition key (car key) is turned on then current from the battery flows through one terminal of the induction coil to primary winding and then to contact- breaker points in the distributor. When the contact breaker points are closed, current propagates through them, turning the primary coil and iron coil into electromagnet while creating a magnetic field. The current then completes its circuit through the body of the car and back to the battery.

Now at this stage if the breaker points open, the circuit is momentarily interrupted to generate high-voltage current in the secondary winding which is then fed through the distributor to spark plug to generate spark in the combustion chamber.


The main function of distributor is to distribute the high voltage from the induction coil to the spark plug in the appropriate cylinder. The timing is very crucial for the engine to perform well. It consists of a rotor which is connected to the coil; the rotor rotates inside the cap and while rotating it transmits high voltage to the cap at specific interval. This happens because its tip comes close to the contact points on the cap. Distributor has one contact point per cylinder. This transmitting (in the form of arc as it never touches each other) of high voltage from rotor to contact point is tuned up perfectly with the power stroke in the cylinder. It contains a condenser (capacitor) which prevents arc thus heating across the contacts point.

The other function of the distributor is to break the current of the coil with the help of contact breaker.

Now let us take a look at how arc is controlled in a distributor. This is done with the help of another part housed in distributor called contact breaker.

Contact Breaker

 Contact breaker is housed with distributor along with a condenser (capacitor). The high voltage produced in primary windings due to magnetic fields causes an arc across the opening contact breaker points. To avoid burning and pitting a condenser is added to suppress the arcing. The capacitor also acts as reservoir for electrical energy. This energy flows back through primary windingand thus speeding the collapse of magnetic field and increasing voltage in secondary winding.

The voltage thus produced travels through high tension wires to spark plug


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