Posted on October 27, 2020 C7 and C9 Industrial Engines Troubleshooting – System Overview System Operation The engine utilizes a Hydraulic Electronic Unit Injector (HEUI) fuel system. A solenoid on each injector meters the amount of fuel that is delivered by the injector. An axial piston pump that is referred to as the unit injector hydraulic pump pressurizes oil in order to activate the injector. An Electronic 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 electronic system for the engine consists of the ECM, the wiring harness, the engine sensors, the switches, the injection actuation pressure control valve, the unit injector hydraulic pump, the HEUI injectors and the interface for a particular application. 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 curves The ECM determines the timing and the amount of fuel that is delivered to the cylinders. This determination is based on the actual conditions and 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 via a signal from the engine speed/timing sensor. If 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 amount of fuel that is injected. 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 smoke Cold mode is activated whenever the engine coolant temperature falls below 18 °C (64 °F). Cold mode remains active until the engine coolant temperature rises above 20 °C (68 °F) or until the engine has been running for 14 minutes. 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 turbocharger outlet pressure. A higher turbocharger outlet pressure indicates that there is more air in the cylinder. When the ECM senses a higher turbocharger outlet pressure, the ECM increases the “FRC Fuel Limit”. When the ECM increases the “FRC Fuel Limit”, the ECM allows more fuel into the cylinder. The “FRC Fuel Limit” is programmed into the flash file at the factory. The “FRC Fuel Limit” cannot be changed. The “Rated Fuel Limit” is a limit that is based on the power rating of the engine and on the engine speed. The “Rated Fuel Limit” is similar to the rack stops and the torque spring on a mechanically governed engine. The “Rated Fuel Limit” provides the power curves and the torque curves for a specific engine family and for a specific engine rating. The “Rated Fuel Limit” is programmed into the flash file at the factory. The “Rated Fuel Limit” cannot be changed. 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 calculates when fuel injection should occur relative to the top center position. The ECM also provides the signal to the injector at the desired time. The ECM adjusts timing for optimum engine performance, optimum fuel economy, and optimum control of white smoke. Injection Actuation Pressure Control System The injection actuation pressure control valve (IAPCV) that is internal to the unit injector hydraulic pump is a precision displacement control actuator. This actuator changes the pump outlet flow that is based on the control current that is supplied by the ECM. The variable displacement unit injector hydraulic pump pressurizes only the amount of high pressure oil that is needed by the injectors. Starting Aids The following devices (if equipped) are used in order to improve the starting of the engine in cold weather conditions. Air inlet heater Ether injection The ECM controls the air inlet heater. The ether injection system can be controlled by the ECM or by the operator. Programmable Parameters Certain parameters that affect the engine operation may be changed with electronic service tools. The parameters are stored in the ECM, and the parameters are protected from unauthorized changes by passwords. Passwords Several system configuration parameters and most logged events are protected by passwords. Refer to programming parameters Troubleshooting, “Customer Passwords” and refer to programming parameters Troubleshooting, “Factory Passwords”.