If you have a 3 cylinder diesel engine and one injector, say, is not working, the engine will sound like a 2 cylinder. If you unscrew one injector at a time and left fuel run out and check for changes in how the engine sounds and runs, you can find which injector, say, is bad. If you find the bad injector and unscrew it, nothing will really change. That injector is your bad one. Everybody agree with my assessment?