The purpose of this bulletin is to provide information regarding a high-pitched ?chirp?, ?squeak? or ?cricket? sound you may hear coming from the engine?s high-pressure fuel pump. Not all pumps may exhibit this condition. Some may have a plunger stopper shape which in combination with certain fuel temperatures or fuel formulations, may result in aeration of the fuel within the body of the pump and cause this sound when the engine is idling. This result is non-detrimental to the fuel system or engine. A production change was made to an internal fuel passage along with a change to the shape of the plunger stopper thus eliminating the source of the sound. Once the sound has been confirmed, the high-pressure pump assembly must be replaced to remedy the condition.
