When the high pressure is relieved from the top of the nozzle needle, high pressure on the lower surfaces force
the needle up and allows fuel to be sprayed into the combustion chamber.
When the control valve is released, spring pressure and high pressure fuel moves the needle back up against the seat in the control valve housing, sealing the nozzle control chamber.
High pressure fuel is again applied to the top of the nozzle needle, pushing the needle down to stop fuel flow into
the combustion chamber.