BUSHING 2131368 - Caterpillar

System Operation
These engines use a HEUI fuel system. The injection pump, the fuel lines and the nozzles that are used in mechanical engines have been replaced with a hydraulic electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. An axial piston pump increases the engine oil pressure in order to activate 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.Electronic Controls
The engine's electronic system consists of the ECM, the engine sensors, the injection actuation pressure control valve, and the vehicle 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 on the engine serve as the engine governor.The electronic controls determine the timing, the injection pressure 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 during starting and operation.The governor uses the accelerator pedal position sensor to determine the desired engine speed. The governor compares the desired engine speed to the actual engine speed. The actual engine speed is determined through the camshaft position sensors. If the desired engine speed is greater than the actual engine speed, the governor injects more fuel in order to increase engine speed.
Illustration 1 g00942969
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
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
Intake manifold air temperature sensor
Atmospheric pressure sensor
Boost pressure sensorThe ECM knows the cylinder position for timing because of the signal from the engine speed/timing sensors. The ECM adjusts timing for optimum engine performance, for fuel economy, and for the control of white smoke. Actual timing and desired timing cannot be viewed on the Caterpillar Electronic Technician Cat ET. The ECM determines the location of top center of the number one cylinder from the signal that is provided by the engine speed/timing sensors. The ECM decides when injection should occur relative to top center. The ECM then provides the signal to the injector at the desired time.Fuel Injection
The ECM controls the amount of fuel that is injected by varying the signals to the injectors and by controlling actuation pressure. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal in order to energize the solenoid. The injector solenoid moves a seated pin that allows the actuation