Series 60 N3 Electronic Unit Injector

Engine models built after December 1, 2003 will use the N3 Electronic Unit Injector (EUI). The N3 injector is designed as an inline concept. The fuel metering unit or module is positioned under the plunger, so the overall envelope of the N3 is smaller than previous injectors. The N3 has an inwardly opening of solenoid valve which controls beginning of injection and end of injection. The solenoid valve closing point defines the beginning of injection (BOI) and the solenoid valve opening point defines the end of injection (EOI). Pressure is generated by the downward movement of the plunger in combination with the closed solenoid valve. Fuel quantity is metered by the length of time the solenoid valve remains closed. A magnetic core is incorporated into the module. The electrical leads from the core are brought to an external position on the injector through a modular two-pin connector socket.

The advantages of the N3 injector are: ‪

• Improved strength.
• Reduced external leakage potential.
• Compact design.
• Reduced weight. The amount of fuel injected and the beginning of injection timing is determined by the ECU. The ECU sends a command pulse which activites the injector solenoid. The N3 EUI performs four functions : ‪
• Creates the high-fuel pressure required for efficient injection.
• Meters and injects the exact amount of fuel to handle the load.
• Atomizes the fuel for mixing with the air in the combustion chamber.
• Permits continous fuel flow for component cooling.

Engine combustion is obtained by injecting, under pressure, a small quantity of accurately metered and finely atomized fuel oil into the cylinder. Metering and timing of the fuel is accomplished by the ECU which actuates the solenoid control valve to stop the free flow of fuel through the injector. When the solenoid control valve closes, fuel is trapped in the injector body and under the plunger. The continuous fuel flow through the injector prevents air pockets in the fuel system and cools those injector parts subjected to high combustion temperatures.