When the car key is turned on, the electricity from the battery travels to the starter and distributor. The starter in the engine uses electric battery power to begin rotating the engine's crankshaft. The electric battery power traveling to the distributor is distributed to all the spark plugs in the engine block.
Once the starter begins to rotate the crankshaft, the pistons in the engine block begin to stroke up and down. When the piston goes down, a fuel injector mists a gas-and-oxygen mixture into the piston chamber. As the piston begins to travel back up, it compresses the gas and oxygen mix. At the top of the stroke, the spark plug fires, and the small combustion fires the piston back down and starts the crankshafts flywheel in a rotating motion.
The flywheel consists of varying weights on opposite sides of the engine's crankshaft. Once the crankshaft makes a full rotation, the varying weights of the flywheel, which are evenly spread out on the crankshaft, will keep the pistons moving up and down. The flywheel will stop rotating once the electrical power is cut to the engine. When the car key is turned off, it breaks the electric circuit from the battery and stops the electrical current traveling to the distributor. Without the distributor distributing electricity to the spark plugs, the pistons will no longer fire downward and keep the flywheel in motion.
