Through the window of the fuel pump housing, it is possible to see the movement of the sleeve up and down. The sleeve has one marking only. At the same time, the sides of the window also have one reference mark. When the reference mark on the sleeve starts moving upward, it indicates that the plunger is moving upward. When the mark on the upward moving sleeve coincides with the mark on the pump body, it indicates that the upward moving plunger has closed the suction port of the fuel pump. This is the beginning of the injection. This can be checked on the flywheel and, if required, can be adjusted and to allow the pump to be timed with the engine. The end of the injection will be dependent on the amount of fuel to be injected.