Hi, i have 2 cargo and just sold a horsebox, they all smoked on start up, if its gray in colour then its sounds like unburnt diesel, some cargo have pre heat on, my old G plate horsebox didnt and that always started but it smoked when it was turning over and when it first started for around 5 mins while the air built up, i replaced the air filtter and diesel filtter and it made no diffrence it went for the mot and it passed on the first emissions test, it always did around 20 mpg, so if yours is ok on mpg and passed the mot i wouldnt worry to much about it, after all it is 17 years old.
james
February 2009