5033644 JOHNSON HOSE, WATER RETURN

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 speed/timing 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 example The 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
Air temperature sensor for the inlet manifold
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 with 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 pressure to hold the nozzle check closed. The movement of the seated pin also causes the spool valve to open. This allows the actuation pressure to act on the piston and on the plunger. This produces injection pressure. The hydraulic force that holds the nozzle check closed quickly dissipates and the injection pressure opens the nozzle check. By controlling the timing and the duration of the high voltage signal, the ECM can control the following aspects of injection:
Injection timing
Fuel delivery
Injection rate shape The ECM controls injection pressure by controlling the injection actuation pressure control valve (IAPCV). The IAPCV controls the pump outlet pressure by moving components within the pump.The personality module inside the ECM sets certain limits on the amount of fuel that can be injected. The "FRC Fuel Limit" is a limit that is based on the boost pressure. The "FRC Fuel Limit" is used to control the air/fuel ratio for control of emissions. When the ECM senses a higher boost pressure, the ECM increases the "FRC Fuel Limit". A higher boost pressure indicates that there is more air in the cylinder. When the ECM increases the "FRC Fuel Limit", the ECM allows more fuel into the cylinder.The "Rated Fuel Limit" is a limit that is based on the power rating of the engine and engine rpm. 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 a specific engine rating. All of these limits are determined at the factory. These limits are in the personality module and these limits cannot be changed. Injection Actuation Pressure Control System
The ECM controls the fuel injection delivery and injection pressure by controlling oil pressure to the fuel injectors. 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 regulates the pump outlet pressure.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's signal is compared by the ECM to the desired injection actuation pressure. The injection actuation pressure sensor's signal is based on sensor inputs. The sensor inputs are used to adjust the control current to the injection actuation pressure control valve in order 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 the high pressure oil manifold. All injectors have a constant supply of oil while the engine is running. Disabling the electrical signal to the injector solenoid does not interrupt the oil flow that is available to the fuel injector.Cold Mode
Cold mode is activated when the coolant temperature is below 18 °C (64 °F). When cold mode begins, the idle rpm speed ramps up to 1000 rpm two minutes after the engine is started. Other features such as "Exhaust Brake Warmup" and "Battery Monitor Elevated Idle" may also affect cold idle speed. Refer to Troubleshooting, "Customer Specified Parameters" for more information on parameters that may affect the idle speed. Cold mode stays active until any of the following conditions are met:
The coolant temperature reaches 18 °C (64 °F).
15 minutes have expired.
The service brake is depressed.
The clutch pedal is depressed.
The automatic transmission