diesel knock i think

hi chaps my 300tdi has a knock which sounds like a diesel knock and i can smell diesel when i walk past the rear of it .so while it was ticking over i cracked off the injector pipes and found when i cracked off number 2 the knock went soon as i nipped it up it came back .when its ticking over it seems to be missing a bit but when i crack off the pipe it dose make a differance. tappets all ok checked them. can anyone help me thanks

change no2 if its weakend it will open too early causing knock and unburnt diesel smell ive got some good second hand ones if you get stuck

hi thanks for that i will have go in the next few days when i get time and let you know the outcome