## Fuel and Emissions Systems

#### System Descriptions (cont'd)

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Fuel System Outline

System Outline

This system also provides the following functions:

- A self-diagnosis and alarm function that uses a computer to diagnose the system' s major components and to alert the driver in case of a problem.
- A fail-safe function to stop the engine, depending upon the location of the problem.
- A backup function to change the fuel regulation method, thus enabling the vehicle to continue operating.

System Configuration

Divided by function, the system can be classified according to the fuel system and the control system.

Fuel System

The high-pressure fuel that is generated by the supply pump is distributed to the cylinders by way of a common rail.

Then, the electromagnetic valves in the injectors open and close the nozzle needle valve to control the starting and ending of the injection of fuel.

Control System

Based on the signals received from sensors that are mounted on the engine and on the vehicle, the ECM controls the timing of the current and the length of time that the current is applied to the injectors, thus ensuring that an optimal amount of fuel is injected at an optimal time.

The control system can be broadly classified according to the following electronic components; sensors, computers, and actuators.

a a a