Set the first oscilloscope input to 100V (full scale).Resistance must be between 0.4 and 0.8 ohms. Connect a precise ohmmeter between the terminals of the injector connector.Disconnect the two-pin injector connector.Make sure ignition is off and the engine is not started.When current to the solenoid is turned OFF, the solenoid valve falls causing the nozzle needle to close immediately and the injection to stop. When current continues to be applied to the solenoid, the nozzle reaches its maximum lift, where the injection rate is also at the maximum level. The fuel that flows below the piston lifts the piston needle upward, which helps improve the nozzle's opening and closing response. The fuel that flows past the outlet orifice flows to the leak pipe and below the command piston. This causes the nozzle needle to rise and the injection to start. After the fuel flows out, the pressure in the control chamber decreases, pulling the command piston up. When current is initially applied to the solenoid, the attraction force of the solenoid pulls the solenoid valve up, effectively opening the outlet orifice and allowing fuel to flow out of the control chamber. This closes the nozzle needle, and as a result, fuel is not injected. For this reason, the hydraulic pressure that is applied to the command piston causes the nozzle spring to compress. Thus, the solenoid valve is pushed downward, effectively closing the outlet orifice. When no current is supplied to the solenoid, the spring force is stronger than the hydraulic pressure in the control chamber. The TWV (Two-Way Valve) solenoid valve opens and closes the outlet orifice to control both the pressure in the control chamber, and the start and end of injection. Principle of operation of the common rail electromagnetic injector 1 shows a typical electromagnetic common rail injector. Some advanced common rail fuel systems perform as many as five injections per stroke.įig.
In order to lower engine noise, the engine's electronic control unit can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimizing injection timing and quantity for variations in fuel quality, cold starting and so on. Common Rail injectors make possible fine electronic control over the fuel injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel atomization.
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