METHOD TO DETERMINE THE COKING OF A FUEL INJECTOR

A method to determine the level of coking in a fuel injector, said injector including a needle valve having a needle adapted to move to and from a first (closed valve) position, where the tip of the needle is in contact with a valve seat, and a second (valve open) position where the needle has moved to its furthest operational point from the valve seat, comprising measuring the duration taken for the needle to move from said first position to said second position and/or vice versa, and comparing this with at least one previous value(s).