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Illustration #110

Rotor arm HT lead The distributor directs the flow of high-tension current from the coil through the rotor arm, and distributes it to each sparkplug in turn. A device called a condenser, fitted on the distributor, ensures that when the points are open there is no sparking across them, which would tend to burn the contact faces. The HT current from the distributor passes down the central core of the sparkplug, then produces a spark as it jumps the gap to the side electrode. This ignires the fuel-air mixture in the cylinder. The coil consists of a metal casing containing two sets of insulated wire windings on a soft-iron central core. The collapse of the magnetic fields generated around the primary windings produces the HT current in the secondary winding which goes through the distributor to the sparkplugs. LT lead Camshaft Distributor cam Contact-breaker points Plug cap on terminal Plug lead The battery is the source of electric power when the engine is stationary. It also supplements the power from the generator when it is not turning fast enough to produce 12 volts. Battery The ignition switch is usually mounted on the steering column or dashboard, and controls the flow of current between the battery and ignition system. Ignition switch Drive The distributor is usually driven direct from the camshaft and is geared to turn at half engine speed. Coil Sparkplug Distributor

Explained in

    How the ignition system works

    The purpose of the ignition system is to generate a very high voltage from the car's 12 volt battery, and to send this to each sparkplug in turn, igniting the fuel-air mixture in the engine's combustion chambers. Read more

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