HEAD 1041949 - 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.This application requires a primary ECM and a secondary ECM. The secondary ECM will be capable of providing full engine power. The two-position manual ECM selection switch will be used to select the desired ECM. The ECM selection switch will not have an OFF position.The primary ECM will be used for all programming except for the electronic trim codes. The primary ECM will communicate all programming to the secondary ECM except for the electronic trim codes. The secondary ECM will accept the electronic trim codes directly from the Cat Data Link. The primary ECM must be used to perform a timing calibration and to accept the engine serial number.Electronic Controls
The electronic system consists of the following components: the ECM, the Electronically Controlled Unit Injectors (EUI), the wiring harness, the switches and the sensors. The ECM is the computer. The flash file is the software for the computer. The flash file contains the operating maps. The operating maps define the following characteristics of the engine:
Horsepower
Torque curvesThe ECM determines the timing and the amount of fuel that is delivered to the cylinders. This is 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 actual engine speed is determined through a signal from the engine speed/timing sensor. The desired engine speed is determined with the following factors:
Throttle signal
Other input signals from sensors
Certain diagnostic codesIf the desired engine speed is greater than the actual engine speed, the ECM injects more fuel in order to increase the actual engine speed.Cold Mode
The ECM limits engine power during cold mode operation and the ECM modifies injection timing 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 signals to the injectors. The injector 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 engine RPM.The flash file inside 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 for control of emissions. The "FRC Fuel Limit" is a limit that is based on the intake manifold pressure. A higher intake manifold pressure indicates that there is more air in the cylinder. When the ECM senses a higher