GEAR 4914626 - Caterpillar

System Operation
This engine is electronically controlled. Each cylinder has an electronic unit injector. The Electronic Control Module (ECM) sends a signal to each injector solenoid in order to control the operation of the fuel injection system.Electronic Controls
The electronic system consists of the following components: the ECM, the Electronic Unit Injectors (EUI), the wiring harness, the switches and the sensors. The ECM is a computer that is used to control the engine. The software for the computer is loaded via the flash file. The flash file contains the operating maps and the performance maps for the engine. These maps define the following characteristics of the engine:
Horsepower
Torque curvesThe ECM calculates the timing and the amount of fuel that is delivered to the cylinders. These calculations are based on the actual conditions and/or on the desired conditions at any given time.The ECM compares the desired engine speed to the actual engine speed. The ECM calculates actual engine speed from signals that are produced by the engine speed/timing sensor. The desired engine speed is calculated by the ECM with the following variables:
Throttle signal
Input signals from engine sensors
Certain diagnostic codesIf the desired engine speed is greater than the actual engine speed, the ECM increases the duration of the fuel injection. This injects more fuel into the cylinders in order to increase the actual engine speed.Cold Mode
The ECM limits engine power during cold mode operation. Injection timing is also modified during cold mode operation. Cold mode operation provides the following benefits:
Increased cold weather starting capability
Reduced warm-up time
Reduced white smokeCold mode is activated whenever the engine temperature falls below a predetermined value. Cold mode remains active until the engine temperature rises above a predetermined value or until a time limit is exceeded.Fuel Injection
The ECM controls the amount of fuel that is injected by varying the duration of the signals to the injectors. The injector will pump fuel only while 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 engine RPM.The flash file that is programmed into the ECM sets certain limits on the amount of fuel that can be injected. The "FRC Fuel Limit" is used to control the air/fuel ratio in order to control emissions. The "FRC Fuel Limit" is a limit that is based on the boost pressure of the engine. A higher boost pressure indicates that there is more air in the cylinder. As the boost pressure increases, the ECM calculates an increased "FRC Fuel Limit". When the "FRC Fuel Limit" is increased, the ECM injects more fuel into the cylinder. The "FRC Fuel Limit" is programmed into the ECM at the factory. This fuel setting cannot be changed by the customer.The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and on engine rpm. The "Rated Fuel Limit" is a fuel