Lever up plunger up no demand for flow
Lever down (or manually pressing the flush lever)
Creates the demand for flow.
At all times the pump is controlled by the pressure system. This is why occasionally when the machine is set idle one boiler will need topping up and you’ll hear the pump activate briefly.
When the small plunger is pressed, all pressure is lost from the system as it opens up flow to the group. Therefore, you have created the demand for flow and for the pressure to be equalised again.
It really is that simple and it is a very clever design.
You’re must unsure either by adjusting the black wedge or the screw at the back of the lever. The plunger is fully pressed when the lever is pulled. The idea of the black wedge is it presses the plunger as soon as you start to move the main lever as opposed to only when the lever is fully down as on the original design giving less, air and more water in the chamber.
With the lever up, the screw at the back of the small lever should be touching but NOT pressing the plunger. Minimal Gap.
If you were silly and tightened the screw down onto the plunger for some reason the pump would run continuously!!