The timing belt, or timing chain in certain cars, is a drive belt that integrates the rotation of the engine’s crankshaft and camshaft with the opening and closing of your engine’s valves. Anytime the crankshaft turns, the timing belt turns the camshaft, which opens and closes the engine valves to allow the pistons to move up and down. Your car’s engine operates in four phases: intake, compression, combustion, and exhaust.
During the intake phase, intake valves open and exhaust valves close as fuel and air enter the cylinders. As the air and fuel is mixed, compressed, and ignited by spark plugs during the compression and combustion phases, the valves close.
The remaining air and fuel is pushed out of the exhaust valve during the exhaust phase. The timing belt is responsible for synchronizing this process and for opening and closing valves during normal engine operation.