Fuel Injection Volume Control

The amount of fuel injected depends on fuel system pressure and the length of time the injector is turned on. Fuel system pressure is controlled by the pressure regulator, and injector on time is controlled by the ECM. The time the injector is on is often called duration or pulse width, and it is measured in milliseconds (ms). Cold starting requires the highest pulsewidth. Pulsewidth is dependent primarily on engine load and engine coolant temperature. The higher the engine load and the more the throttle is opened to let air in, the greater pulsewidth increases. The ECM determines the duration based on the input sensor signals, engine conditions, and its programming.

Start Mode

When the ignition switch is in the Start position, the ECM receives a voltage signal at the STA terminal. The ECM determines basic injection duration based on the ECT (THW) signal. On MAP sensor equipped engines the ECM will then modify this duration based on the IAT (THA) signal.

Start Mode

When the ignition switch is in the Start position, the ECM receives a voltage signal at the STA terminal. The ECM determines basic injection duration based on the ECT (THW) signal. On MAP sensor equipped engines the ECM will then modify this duration based on the IAT (THA) signal.

The ECM will adjust the duration based on battery voltage. During cranking, battery voltage is much lower causing the injector valve to lift slowly. The ECM corrects for this by increasing injection duration.

When the ECM receives the NE signal (Crankshaft Position Sensor), all the injectors are turned on simultaneously. This insures there is enough fuel for starting the engine. Note that below freezing, injection duration increases drastically to overcome the poor vaporization characteristics of fuel at these temperatures.

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Responses

  • suzanne
    How injection volume controlled?
    1 year ago

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