Originally Posted by TQA
It is a long time ago but my memory says the data came from the Midland Bus Company and a London company and was from large number of vehicles and a decade or so of records. The engines would almost certainly have been Gardiners.
Depending on how long ago you mean (Gardiner indicates it was in the days of Leyland buses), there was a time probably 30 years or more ago where tips were serviced and spray patterns could be manually adjusted and many of these adjustments were done using a simple hand pump. Also the spray pattern was a matter interpretation, often by technicians who never really understood the requirement. Under those conditions it was easy to get it wrong and this did happen.
But as injector pressures have increased (some modern injectors break at over 30,000psi these days) tips are not repaired/adjusted, they're simply replaced and that eliminates almost completely the failure rate of serviced injectors. At least that is my experience, YMMV.