RING 0961800 - Caterpillar

System Operation
The fuel system for this engine uses Hydraulic Electronic Unit Injectors (HEUI). The injection pump, the fuel lines and the nozzles that are used in mechanical engines have been replaced with an hydraulic electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. High pressure engine oil is used to operate the injector. An Engine Control Module (ECM) sends a signal to the injection actuation pressure control valve in order to control injection pressure. Another electrical signal is sent to each injector solenoid in order to inject fuel into the cylinders.Electronic Controls
The engine's electronic system consists of the ECM, the engine sensors, the fuel injection system, and the vehicle interface. The ECM is used to control the operation of the engine. The ECM flash file contains the software that is used to program the ECM. The flash file contains the operating maps that define the following characteristics of the engine:
Horsepower
Torque curves
Engine speed (rpm)Engine Governor
The ECM provides the functionality of the engine governor.The ECM determines the timing, the duration and the pressure of injection. The amount of fuel that is delivered to the cylinders is precisely controlled by the ECM. This control is based on the actual conditions and the desired conditions at any given time during starting and operation of the engine.An accelerator pedal position sensor is used to determine the desired engine speed. The ECM compares the desired engine speed to the actual engine speed. The actual engine speed is calculated from signals that are generated by the engine speed/timing sensors. If the desired engine speed is greater than the actual engine speed, the ECM adjusts the signal that is sent to the injectors and the fuel system's high pressure oil pump in order to reduce the engine speed. The ECM continuously monitors the engine for actual conditions in order to adjust for desired conditions.
Illustration 1 g01120999
Typical exampleThe desired engine speed is typically determined by one of the following conditions:
The position of the accelerator pedal
The desired vehicle speed in cruise control
The desired engine rpm in PTO controlTiming Considerations
The ECM determines the fuel injection timing. In addition to desired engine speed and actual engine speed, the following inputs are used by the ECM in order to calculate the engine timing:
Coolant temperature
Intake manifold air temperature
Atmospheric pressure
Boost pressureThe signal from the engine speed/timing sensor is used by the ECM to determine the orientation of the crankshaft. This signal is used by the ECM to calculate an output for the injector solenoids relative to the top center position of each piston. The injection signal is adjusted for optimum engine performance, for fuel economy, and for the control of white smoke. The injection signal is output to each injector solenoid at the optimum time.Fuel Injection
The ECM controls the injection timing and injection duration by varying the output signals to the injectors. The injectors pump fuel into the cylinder only while the injector solenoid is energized. The ECM outputs a high