Diesel Engine Control System Injector Overview


The signals from the ECU are amplified by the EDU to operate the injector. High voltage is used particularly when the valve is open in order to open the nozzles. The injection volume and timing are controlled by adjusting the opening and closing timing of the injectors, just as in the EFI system of a gasoline engine.

Injection volume control

Injection timing control

Construction of Injector

Correction Resistor of Injector

Given the same injection interval, mechanical variances will still cause the injection volume from injector to injector to vary. To enable the ECU to correct these variances, the injectors are provided with a correction resistor for each injector. Based on information received from each correction resister, the ECU corrects the variances in injection volume between the injectors. These correction resistors are provided to enable the ECU to identify the injectors, and are not connected to the injector circuit.


The correction resistor,which is listed above, is not attached to the injector of 1ND-TV E/G. 3 types of injectors are adopted based on the difference of the injection volume, and the indentification numbers (A, B, C) are attached on the top of each injector.

Types of Injector Correction Resistor for 1CD-FTV E/G

There are 25 types of injectors as indicated below, each provided with a different correction resistor. When replacing an injector, the ECU automatically makes the proper fuel correction, so it is not necessary to replace it with one with the same correction resistance.

Injector Operations

1. Before the injector operation

The fuel that has been fed from the common-rail separates into the control chamber and the bottom of the needle. In this state, the needle is pushed down by the pressure in the control chamber and by the spring, and the nozzle remains closed.

2. When the solenoid valve opens

When the actuating voltage is applied by the ECUEDU, the solenoid valve opens and the pressure in the control chamber decreases.

3. When the needle opens

Due to the operation of the orifice, the pressure at the bottom of the needle remains high, and the nozzle opens to inject fuel.

4. When the solenoid valve closes

When the voltage applied by the ECU-EDU ends, the spring force causes the solenoid valve to close and the pressure in the control chamber increases again.

5. When the needle closes

Due to the pressure in the control chamber and the force of the spring, the needle descends and closes the nozzle to end the injection.

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