Basic ignition system

Basic Ignition System

Purpose

The ignition system in a gasoline engine creates a spark to ignite the air–fuel mixture in each cylinder. An ignition coil raises the electrical voltage and delivers it to the spark plugs, which produce the spark.

Types of Ignition Systems

• Glow-plug ignition: Described as an old, obsolete approach. According to the subtitles, it could cause uncontrolled combustion and incomplete burning, resulting in higher exhaust emissions.
• Magneto ignition: Uses a magneto as its own electrical generator, so it does not require a battery. It sends current through an ignition coil and distributor to the spark plugs in the engine’s firing order. Because it depends on engine speed, starting can be difficult at low speeds. It is used in some small engines, such as those in scooters, motorcycles, and small motorboats.
• Battery ignition: Uses the battery as its electrical source. The video discusses a conventional version with mechanical contact-breaker points.
• Electronic ignition: Uses sensors and electronic circuits—often including transistors and an electronic control module—to switch the ignition current and time the spark. The video presents it as a more precise approach that can support better combustion, including burning leaner mixtures, and potentially improve fuel economy and emissions.

Main Components of a Battery Ignition System

• Battery: Supplies electrical energy to the ignition system. The subtitles mention lead-acid and alkaline batteries.
• Ignition switch: Turns the ignition circuit on or off by connecting the battery to the primary circuit.
• Ballast resistor: Connected in series with the coil’s primary winding. Its resistance rises as it heats, reducing current and helping prevent the primary winding from overheating.
• Ignition coil: A transformer with primary and secondary windings around an iron core. It raises the battery’s low voltage to the much higher voltage needed for a spark.
• Contact breaker: Mechanical points that open and close the primary circuit. When they open, the current is interrupted, triggering the coil to generate high voltage.
• Spark plugs: Create sparks across a gap between electrodes inside the cylinders, igniting the air–fuel mixture.
• Distributor: Routes high-voltage pulses to the spark plugs in the engine’s firing order and at the appropriate time. The video also describes timing-advance mechanisms and two distributor designs: a brush type and a rotor that passes close to, but does not touch, the cap contacts.

How the Systems Work

Battery Ignition

With the ignition switch on, current flows from the battery through the ballast resistor and the coil’s primary winding, creating a magnetic field. When the contact breaker opens, the primary current is interrupted and the magnetic field collapses, inducing high voltage in the secondary winding. The distributor then routes that voltage to the appropriate spark plug, where it jumps the electrode gap and ignites the mixture.

Electronic Ignition

A pickup coil senses the position of a rotating reluctor and sends signals to an ignition module. In response, the module switches current in the coil’s primary circuit. The resulting change in the magnetic field induces high voltage in the secondary winding, and the distributor delivers it to the correctly timed spark plug. The subtitles give an approximate output of up to 50,000 volts for this system.

Frequently Asked Questions Covered

• What is the starting system? It turns the crankshaft so the engine can begin its operating cycle.
• What are common ignition-system problems? A faulty coil, spark plug, or plug wire may cause rough running, misfires, reduced fuel economy, or a check-engine warning.
• What can cause ignition failure? The subtitles identify a worn, degraded, or failed spark plug as a common cause. More generally, failure to produce a timely spark prevents the mixture from igniting properly.
• Why might an ignition coil get hot? The video attributes this to excessive current, potentially caused by spark plugs or wires having less resistance than expected.
• How does the video suggest checking an ignition switch? Insert the key and try to crank the engine. If the engine cranks, the subtitles say the switch is working. If it does not crank and a click is heard, the video says the ignition switch may not be the problem.

Speakers and Sources Featured

• Speaker: An unnamed narrator delivering the educational explanation.
• Source: The video is from the Automotive Explained channel. No other named speakers or sources are identified in the subtitles.