MOTOR AS-GOVERNOR 7Y3991 - Caterpillar

System Operation
The electronic system consists of the following components: Electronic Control Module (ECM), Hydraulic Electronic Unit Injectors (HEUI), Injection Actuation Pressure Control Valve (IAPCV), wiring harness, switches and sensors. The ECM receives information from the sensors and the switches on the engine. The ECM processes the information that is collected in order to make decisions on control of the engine. By altering the fuel delivery of the injectors, the ECM controls the speed and the power that is produced by the engine.Electronic Control System
The ECM consists of two main components:
Control computer (hardware)
Personality module (software)
Illustration 1 g00648808
Personality moduleThe control computer is the microprocessor and the electronic circuitry. The personality module contains the software for the control computer. The software contains operating maps that define the following characteristics of the engine:
Horsepower
Torque curves
Engine speedEngine Governor
Illustration 2 g00882872
Diagram of the electronic governorThe ECM governs the engine speed by controlling the amount of fuel that is delivered by the injectors. Refer to Illustration 2. The desired engine speed is determined by input from the throttle switch. Actual engine speed is measured by the engine speed/timing sensors. The ECM changes the amount of fuel that is injected until the actual engine speed matches the desired engine speed.Fuel Injection
Illustration 3 g00648838
Block diagram for the fuel systemThe ECM controls the timing, the duration, and the pressure of the fuel that is injected. The ECM controls the timing and the duration by varying the signals to the injectors. The injectors will inject fuel only if the injector solenoid is energized by a 105 volt signal from the ECM. By controlling the timing and the duration of the 105 volt signal, the ECM can control the timing of the injection and the ECM can control the amount of fuel that is injected. The ECM modulates the injection pressure by varying the signal to the Injection Actuation Pressure Control Valve (IAPCV). The IAPCV controls the pressure of the high pressure oil. The high pressure oil pressurizes the fuel that is in the injectors. By controlling the signal to the IAPCV, the ECM controls the pressure of the fuel that is injected into the engine.The ECM limits engine power and the ECM modifies injection pressure and injection timing during Cold Mode operation. Cold Mode operation has the following benefits: increased startability, reduced warm up period and reduced white smoke. Cold Mode is active if the engine oil temperature falls below a predetermined value and other conditions are met. Cold Mode remains active until the engine has warmed or until a time limit has been exceeded.The personality module inside the ECM sets certain limits on the amount of fuel that can be injected. The FRC Limit is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. The FRC Limit is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher boost pressure, the ECM increases the FRC Limit. A higher boost