They’re smaller than your thumb, inject a metered amount of fuel into each cylinder of your fuel-injected engine and rarely cause problems, but their maintenance needs should be understood as part of knowing the whys of your engine’s operation.
Fuel injection was developed to overcome some of the disadvantages of carburetors, notably unequal distribution of the fuel-air mixture to the cylinders. Currently, there are two fuel injection systems used commonly in our GA airplanes, Bendix-RSA and Continental Motors.