...to go ahead and pull them and see. You can have them "pop" tested for very little money and then you will know. After noticing more black smoke than usual I pulled our injectors this spring at 1200 hours and found them to be in great condition with the exception of one that opened just a little early. Just the act of testing them cleaned the injector of whatever was ailing it. I couldnt get parts quickly so I just replaced the seals and re installed them. Smoke went away and everything is happy again. Our engine is a 3 cylinder 40 hp Yanmar.
Bruce