Ignition System Operation

The ignition system supplies high-voltage surges to the spark plugs in the engine cylinders. These surges produce electric sparks across the spark plug gaps. The heat from the sparks ignites, or sets fire to, the compressed air-fuel mixture in the combustion chambers. When the engine is idling, the spark appears at the plug gap just as the piston nears Top Dead Center (TDC) on the compression stroke. When the engine is operating at higher speeds, or with part throttle, the spark is advanced. It is moved ahead and occurs earlier in the compression stroke. This gives the compressed mixture more time to burn and deliver its energy to the pistons.