(1.1) Injection not taking place
• With the magnet not energized, the armature plate is pushed up by the valve spring such that the ball seat is closed.
• The high-pressure fuel acts upon the control chamber via orifice Z. The same pressure acts upon the nozzle needle.
• The fuel pressure acting on the nozzle needle cannot overcome the valve piston and nozzle spring, so the nozzle needle stays in its downward-pushed position and injection does not take place.
(1.2) Start of injection
• When the magnet is energized, the resulting electromagnetic force draws the armature plate upward, causing the ball seat to open.
• Fuel in the control chamber passes through the ball seat and orifice A and flows to the fuel tank.
• With the pressure in the control chamber reduced, the fuel acting on the nozzle needle overcomes the valve piston and nozzle spring, pushing up the nozzle needle such that injection starts.
• If the magnet remains energized, the injection reaches its maximum level.
(1.3) End of injection
• When energization of the magnet is stopped, the armature plate is pushed downward by the valve spring such that the ball seat closes. At this time, fuel flows into the control chamber via orifice Z, pushing down the valve piston and nozzle needle such that injection finishes.