The ignition system is divided into 2 circuits: high and low voltage. Low voltage circuit (sometimes also called primary) consists of a battery, ignition switch, primary winding of the ignition coil, contact breaker and capacitor (the last two are in the distributor).
The high voltage circuit consists of the secondary coil winding, the spark plug wire leading from the center of the coil to the center of the distributor cap, the rotor, and the spark plug wires leading to the spark plugs.
The ignition system works as follows. The low voltage from the battery is converted into high voltage in the ignition coil, the value of which is sufficient to cause a spark to jump between the spark plug electrodes when there is high compression in the cylinders (provided that the ignition system is in good condition and properly adjusted).
On most models, the ignition wiring harness includes a high-resistance wire in the supply circuit to the ignition coil. Therefore, when replacing a coil, only use a coil with a ballast resistor. When the engine is started, the ballast resistor is shunted and battery voltage is applied to the coil. Therefore, during a cold start of the engine, when the starter consumes a large current, the coil still receives voltage sufficient for a spark to jump between the spark plug electrodes. When the engine is already running, 12 V from the battery first passes through the ballast resistor and only then goes to the coil.
The ignition timing is adjusted mechanically (centrifugal) and vacuum regulators. The mechanical regulator consists of two weights, which, as the engine speed increases, move further and further away from the distributor shaft under the action of centrifugal force.
The vacuum ignition regulator consists of a diaphragm, one side of which is connected by a narrow tube to the carburetor, and the other side to the contact breaker plate. The vacuum in the intake manifold and carburetor, which changes depending on the engine speed and the throttle opening, causes the diaphragm to move, which in turn leads to the movement of the contact breaker plate and, accordingly, the acceleration or deceleration of the ignition timing.
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