Simms Fuel Injector Pump

The excess fuel device works differently in the two pumps. On the vacuum governed one its a spring loaded stop that fits in a slot in the rack. All that happens when you push the button is you move the stop to one side and the governor spring moves the rack back about 1/8". When the engine starts, the governor pulls the rack forward and the excess fuel stop flys back into position.

Its more complicated on the Minimec. To get the button to stay in you have to open the throttle. This can sometimes not fly out when the engine starts. This jams the rack in the stop position or does not allow it to move very far. The engine may run and stop then not start or it may sound normal then cut out when you put it into work. If this happen, a pull on the button with a pair of pliers or grips and some WD40 will sort it out.