Operation

Unit injectors, working phases

Filling phase

During the filling phase, the pump piston (2) is moving up to its top position.

The camshaft high point is passed and the cam follower is moving towards the base of the cam.

The fuel valve (1) is open and fuel can flow into the pump cylinder from the lower fuel passage in the cylinder head and into the injector unit pump cylinder.

Filling continues until the pump piston reaches its top position.

Spill phase

The spill phase begins when the camshaft is turned to the position where the cam, via the rocker arm, begins to press the piston (2) down.

Fuel can now flow through the fuel valve (1), through the hole in the injector and out through the fuel passage. The spill phase continues as long as the fuel valve (1) is open.