The fuel injector injects a precise amount of 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. A fuel injector pump replacement is needed usually when the fuel injector becomes clogged due the fuel filter not being replaced when needed.
When replacing the fuel injector, a technician removes the fuel line to relieve pressure. Most vehicles have more than one fuel injector. On some vehicles, each injector can be removed separately. On other vehicles, the technician must remove several fuel injectors at the same time to gain access to one specific injector. When a fuel injector is replaced the seals must be replaced as well in order to prevent fuel leaks which can cause a fire.
Most manufacturers cover the cost of fuel injector replacement under their factory bumper-to-bumper warranty and there are extended warranties that will cover the cost as well, depending upon the level of coverage selected. However, if the fuel injector fails because the fuel filter was not changed when the manufacturer recommended, then the factory warranty and extended warranty will not cover the cost.