The fuel injector "injects" gas under pressure into the intake manifold. The engine then sucks the gas in, and it is ignited. The ensuing explosion is part of the process the engine uses to create power.
For an engine to operate, it needs gas (fuel) to burn. This burning gas is converted into energy.
Based on calculations made by the on-board fuel injection control computer, the fuel injector injects a precise amount of gas into the engine. The computer analyzes the outside air temperature, the amount of air being drawn into the engine, the temperature of the engine, and many other parameters before deciding exactly how much gas to inject into the engine.
Water and dirt are very harmful to a fuel injector. It is important to change the fuel filter periodically. Adding fuel injection cleaner to the gas tank when refueling may prevent fuel injectors from becoming clogged, which adversely affects drivability and fuel economy, as well as the vehicle's pollution output.
To replace a fuel injector, the fuel line to the injector is removed to relieve fuel pressure. On some vehicles, each injector can be removed from the engine separately. On others, the injectors share a common gas supply, meaning the technician must remove several fuel injectors at the same time to gain access to one specific injector. Any time an injector is removed or replaced, all fuel injector seals are replaced to eliminate the risk of fuel leaks that could cause a fire.