what tweak'e said terrano monster,exactly right,my td27 d21 had 180000k on it when i got it and was blowing clouds of black smoke,the pump was leaking out of the seals,lucky for me it was when the fuel company's where fixing the pump's because of the new low sulphur diesel,the diesel shop that did the pump up for me said the previous owner must have cranked the pump up himself,hereckoned it was way out,reckons they do it to try to get more speed out of them,after they did the pump,just cleaned the injectors,no smoke,economy,has 290000k on it now and still runs like a watch,that's the trick getting them tuned properly.