 If it goes thud, thud, thud, and the other ones that are working go tink, tink, that injector's clogged. Or if it does nothing, if it's like nothing, nothing, and then that third one goes click, click, click, click, click, then those injectors aren't working. So at least you can find out, are the injectors turning on? And if they're a sharp, crisp sound like the ones that work, they're clean and flowing. If they are not, then they're dirty and they're not working. And sometimes those two on the end of the rail like that could change.