F 350 4WD Super Duty V8-6.4L DSL Turbo (2008)
End of Main Injection Step 2
^ When the Engine Control Module (ECM) determines that the correct injector on time has been reached it switches the polarity of the piezo actuator
(1) which causes the piezo discs to return to a non-energized state.
^ Switching the polarity of the piezo actuator (1) enables the valve mushroom (4) to seat via spring pressure and completely block the bored passage
that connects the high pressure fuel to the fuel return line.
^ Seating the valve mushroom (4) allows the pressure to build in the control piston chamber (2) and equal that in the high pressure chamber (3).
^ Once these two chambers have equalized in pressure the downward force (F1) of the control valve will overcome the upward force (F2) of the nozzle
needle due to the larger surface area of the control valve.
^ The control valve then moves downward effectively closing the nozzle needle (5) blocking any fuel from entering the combustion chamber.
