F695042 Force CABLE, GROUND

Electronic Controls
The 3126 HEUI Industrial Engines electronic system consists of the Electronic Control Module (ECM), Engine Sensors, Injection Actuation Pressure Control Valve, and Vehicle Interface. The ECM is the computer which controls the 3126 HEUI engine. The Personality Module in the ECM contains the software which controls how the ECM behaves (the personality module stores the operating maps that define power rating, torque curves, rpm, etc).
Figure 1.1 - Personality ModuleEngine Governor
The Electronic Control system on the 3126 HEUI engine serves as the engine governor. The Electronic Control system determines when and how much fuel to deliver to the cylinders, as well as injection pressure based on the actual and desired conditions at any given time during starting and operation.Basic Governor
The basic governor operation considers the desired and actual conditions, and then takes action to best accommodate the desired conditions.The desired conditions are typically the position of the accelerator pedal, desired vehicle speed when in cruise control, or desired engine rpm when in PTO control. The actual conditions are based on current operating conditions such as coolant temperature, load conditions, etc.Timing Considerations
Once the ECM has determined how much fuel is required, it must next determine when to inject the fuel. Injection timing is determined by the ECM after considering input from the Coolant Temperature Sensor, Inlet Manifold Air Temperature Sensor, and Turbocharger Compressor Outlet Pressure Sensor.The ECM knows the cylinder position for timing because of the signal from the Engine Speed/Timing Sensors. The ECM adjusts timing for best engine performance, fuel economy and white smoke control. Actual and Desired Timing cannot be viewed with an Electronic Service Tool.The ECM knows where top center on cylinder #1 is from the signal provided by the engine Speed/Timing Sensors. The ECM decides when injection should occur relative to top center and provides the signal to the injector at the desired time.Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will pump fuel only if the injector solenoid is energized. The ECM sends a high voltage signal to energize the solenoid. The energized solenoid lifts the poppet off its seat, closing the oil path to drain and opening the inlet for the high pressure oil. The high pressure oil enters the injector and acts on an intensifier piston, increasing the pressure and injecting fuel. By controlling the timing and duration of the high voltage signal, the ECM can control injection timing and the amount of fuel injected.The ECM also controls the pressure of the fuel injected into the cylinder by controlling the injection actuation pressure control valve. The injection actuation pressure control valve is a dump valve closely controlling the output pressure of the high pressure oil pump.Personality Module
The Personality Module inside the ECM sets certain limits on the amount of fuel that can be injected. FRC Fuel Pos is a limit based on Turbocharger Compressor Outlet pressure to control the air/fuel ratio for emissions control. When the ECM senses a higher Turbocharger Compressor Outlet pressure (more air into cylinder), it increases the FRC Fuel Pos limit (allows more fuel into cylinder). Rated Fuel Pos is a limit based on the power rating of the engine and rpm. It is similar to the rack stops and torque spring on a mechanically governed engine. It provides power and torque curves for a specific engine family and rating. All of these limits are determined at the factory in the Personality Module and cannot be changed in the field. Injection timing depends on engine rpm, load and other operating factors.Injection Actuation Pressure System
The ECM controls fuel injection by controlling oil. The pressure of the oil in the high pressure oil manifold is controlled by the ECM through control of the injection actuation pressure control valve. The injection actuation pressure control valve (dump valve) controls the high pressure pump outlet pressure by dumping excess flow back to the oil sump.The ECM monitors the pressure in the high pressure manifold through the Injection Actuation Pressure Sensor. The injection actuation pressure sensor is located in the top of the manifold on the left side of the engine. The injection actuation pressure sensor signal ( Inj Act Pr) is compared by the ECM to the desired injection actuation pressure ( Des Inj Act Pr). The ECM determines the Des Inj Act Pr based on several inputs and changes the position of the injection actuation pressure control valve ( Inj Act Output) to adjust the oil pressure in the high pressure manifold.High pressure oil is routed from the pump to the high pressure manifold through a steel tube. From the manifold the oil is routed to each injector through short jumper tubes. All injectors have a constant supply of oil while the engine is running. Cutting out an injector disables the electrical signal to the injector solenoid, but does not interrupt the oil flow to the injector.Customer Parameters Affect on Engine Governing
A unique feature of Electronic Engines is Customer Specified Parameters. These parameters allow the vehicle owner to instruct the ECM how to fine tube the engine operation to accommodate the typical usage of the vehicle, and to match the power train of the vehicle.Many of the Customer Parameters provide additional restrictions on the "Required Action" the ECM will take in response to the operators' input.Some parameters are intended to notify the operator of potential engine damage (Engine Monitoring Parameters). Some parameters enhance fuel economy (Vehicle Speed, Cruise Control, Engine/Gear Limits and Idle Shutdown Parameters). Other parameters are provided to enhance the engine installation or provide engine operation information to the vehicle owner.Engine Monitoring
Caterpillar provides a factory installed Engine Monitoring system. The Caterpillar Engine Monitoring system monitors engine coolant temperature. The Coolant Temperature Sensor is standard on all engines.Caterpillar Engine Monitoring can be programmed to three different modes (OFF, , or DERATE) through a Customer Parameter. The Coolant Temperature Sensor will operate in the Engine Monitoring Mode selected. Excessive coolant temperature will not shut down the engine.Caterpillar Engine Monitoring OFF Operation
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