Fuel injectors are in all modern vehicles but you have probably not played with one since it is not a common replacement item. Jeremy Lang demonstrates his Fuel Injector Test system and shows off how an injector works. If you are interested in building your own Jeremy has made the build details available here (https://www.dropbox.com/sh/lw8dl8vt7igtgxh/AADgvF_Ska-24dXnZktGyuZPa?dl=0).