SWITCH AS-PRESSURE 4592594 - Caterpillar

Illustration 1 g00669770This engine was designed for electronic control. Each cylinder has an electronic unit injector. A solenoid on each injector controls the amount of fuel that is delivered by the injector. The Electronic Control Module (ECM) sends a signal to each injector solenoid in order to provide complete control over the operation of the fuel injection system.Electronic Controls
The electronic system consists of the following components: the ECM, the mechanically actuated electronically controlled unit injectors (MEUI), 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. These decisions are based on the actual conditions and/or 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 through the following items:
Throttle position sensor
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.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.Once the ECM determines the amount of fuel that is required, the ECM must determine the timing of the fuel injection. The ECM determines the top center position of each cylinder from the engine speed/timing sensor's signal. The ECM determines 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 optimum engine performance, for optimum fuel economy, and for optimum control of white smoke.Programmable Parameters
Certain parameters that affect the engine operation may be changed with the Caterpillar Electronic Technician (ET). The parameters are stored in the ECM, and some parameters are protected from unauthorized changes by passwords.Passwords
Several system configuration parameters and most logged events are protected by factory passwords. Factory passwords are available only to Caterpillar dealers. Refer to Troubleshooting, "Factory Passwords" for additional information.