Chapter VI - The ignition and starting system

The ignition system

It has the role of igniting the fuel mixture and consists of all the elements that produce and distribute the electric current necessary (for engines with spark ignition) for forming the electric spark.
​In modern cars, due to the fact that the engines achieve high speeds, power and compression ratios, electronic ignition is used by excluding the breaker and even the induction coil and the distributor.

The electronic ignition systems can be:

• with transistors and mechanical breaker;
• with transistors and mechanical or photoelectric breaker.

The ignition system consists of:

- the accumulator battery: has the role of a source of electric energy that supplies for a short time the electric equipment, when the electric energy generator does not work or when it cannot cope alone;

- the key switch: has the role of supplying the ignition and starting circuit (through the starter);

- the induction coil: acts on the autotransformer principle, having the role of transforming the low-voltage current received from the accumulator battery (12V) into high-voltage current (15000 … 20000V), capable of piercing the space between the spark plug electrodes to obtain the electric spark.

- the breaker-distributor: which consists of: 

• the actual breaker: interrupts and contacts the primary circuit of the ignition system;
• the distributor of the high voltage to the spark plugs: distributes the high-voltage current to the spark plugs mounted on the cylinders, in the preset ignition order;
• the condenser: has the role of storing the electric energy produced by the self-induction of the primary winding;
• the advance regulators: automatically adjust depending on speed and load, the ignition advance, with the help of the centrifugal advance regulator and the vacuum advance regulator.

- the spark plug: serves to produce the electric sparks necessary for igniting the fuel mixture;

- the glow plug: is a nickel-chrome spiral that heats up when the electric circuit is closed, allowing the heating of the air that enters the cylinders;

- the starting motor: is a direct current electric motor, which serves to rotate the crankshaft for starting the engine of the motor vehicle, transforming the electric energy into mechanical energy.

The starting system

It forms the energy necessary for the crankshaft of the engine to be rotated and thus for the engine to be started, ensuring that the starting speed of the crankshaft is appropriate for igniting the fuel mixture, for engines with spark ignition, or for the fuel injection pressure, for engines with compression ignition.

The starting of the engine with the help of an electric motor (starter) of direct current, which couples with the toothed ring located on the flywheel of the crankshaft with the help of the drive pinion mounted on the starter shaft.

The starter, also called the starting motor, is a direct current motor powered by the accumulator battery. Its operating principle is based on the phenomenon of electromagnetic induction.