COWLING AS 3147007 - Caterpillar

System Operation
The engines were designed for electronic control. The injection pump, the fuel lines and the nozzles that are used in mechanical engines have been replaced with an electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. An Electronic Control Module (ECM) sends a signal to each injector solenoid in order to provide complete control of the engine.Electronic Controls
The electronic system consists of the Electronic Control Module (ECM), the engine sensors, and the Machine Interface. The ECM is the computer. The personality module is the software for the computer. The personality module contains the operating maps. The operating maps define the following characteristics of the engine:
Horsepower
Torque curves
Engine speed (rpm)Engine Governor
The electronic controls determine the timing and the amount of fuel that is delivered to the cylinders. These decisions are based on the actual conditions and the desired conditions at any given time.The governor compares the desired engine speed to the actual engine speed. The actual engine speed is determined through the crankshaft position sensor. If the desired engine speed is greater than the actual engine speed, the governor injects more fuel in order to increase engine speed.Timing Considerations
Once the governor has determined the amount of fuel that is required, the governor must determine the timing of the fuel injection. Fuel injection timing is determined by the ECM after considering input from the following components:
Coolant temperature sensor
Inlet air temperature sensor
Atmospheric pressure sensor
Turbocharger outlet pressure sensorAt start-up, the ECM determines the top center position of the number 1 cylinder from the camshaft position sensor's signal. After start-up, the ECM determines the top center position of the number 1 cylinder from the crankshaft position sensor. The ECM decides when fuel injection should occur relative to the top center position and the ECM provides the signal to the injector at the desired time. The ECM adjusts timing for the best engine performance, the best fuel economy and the best control of white smoke. Actual timing cannot be viewed with an electronic service tool. Also, desired timing cannot be viewed with an electronic service tool.Fuel Injection
The ECM controls the amount of fuel that is injected by varying the signals to the injectors. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal to the solenoid. This high voltage signal energizes the solenoid. By controlling the timing and the duration of the high voltage signal, the ECM can control injection timing and the ECM can control the amount of fuel that is injected.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 turbocharger outlet pressure. The FRC Limit is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher turbocharger outlet pressure, the ECM increases the FRC Limit. A higher turbocharger outlet pressure indicates that there is