establish the timing sequence. The engine is fitted with a variety of sensors and switches to gather the following information:

Intake air temperature

Engine speed

Manifold vacuum

Engine coolant temperature

Throttle valve position

Intake manifold airflow

The computer receives this information and uses it to calculate the amount of fuel delivered at each injection cycle. The computer is capable of changing the rate of fuel delivery to the engine hundreds of times a second, making the system extremely accurate. The computer regulates the amount of fuel delivered by varying the duration of injector operation.

CONTINUOUS FUEL INJECTION SYSTEMS

Continuous fuel injection systems (fig. 5-3) provide a continuous spray of fuel from each injector at a point before the intake valve. Because the entrance of the fuel into the cylinder is controlled by the intake valve, the continuous system will fulfill the requirements of a gasoline engine. Timed injection systems, though a necessity on diesel engines, cost more than continuous systems. They are used on gasoline engines only when more precise fuel metering is desired.

Figure 5-3.-Continuous injection.