Automotive Systems

Formerly Automotive Systems I

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Continuous Fuel Injection System


Continuous fuel injection systems (fig. 4-45) provide a continuous spray of fuel from each injector at a point in the intake port located just before the intake valve. Because the entrance of the fuel into the cylinder is controlled by the intake valve, the continuous system fulfills the requirements of a gasoline engine.

Basic operation of a continuous fuel injection is as follows:

  1. Fuel is fed to the system by an electric fuel pump that delivers fuel to the mixture control unit. A fuel pressure regulator maintains fuel line pressure and sends excess fuel back to the tank.
  2. The mixture control unit regulates the amount of fuel that is sent to the injectors based on the amount of air flow through the intake and the engine temperature. The unit is operated by the air flow sensing plate and warm-up regulator.
  3. The accelerator pedal regulates the rate of air flow through the intake by opening and closing the throttle valve.
  4. A cold-start injector is installed in the intake to provide a richer mixture during engine start-up and warm-up. It is actuated by electric current from the thermal sensor any time the temperature of the coolant is below a certain level.

The injector for a continuous fuel injection system is a simple spring-loaded valve. It injects fuel all the time the engine is running. A spring holds the valve in a normally closed position with the engine OFF. This action keeps fuel from dripping into the engine. When the engine STARTS, fuel pressure builds and pushes the injector valve open. A steady stream of gasoline then sprays toward each intake valve. The fuel is pulled into the engine when the intake valves open.

Figure 4-45.—Continuous fuel injection system.
Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

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