Thanks for the reply. You confirmed what I suspected in the closed loop aspect. However, one of the fuel pump tests in the MB manual indicates that a too low pressure rate calls for pump replacement. Too High pressure also calls for replacement of the pump. Getting back to the pump model number differences, do some pumps generate more pressure? My real question is the 190E and the 300E and the 380 SEL all have different part numbers even though dimensionally they all appear alike? What then is the difference? What happens when the pump pressure is too high? What are the symptoms?
82 380 SEL
84 300 SD