SEAL-O-RING 9X7725 - Caterpillar

System Operation
The C-10, C-12, and C-15 Truck Engines were designed for electronic control. The injection pump, the fuel lines and the nozzles that are used in mechanical engines have been replaced with an electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel that is delivered by the injector. An Engine Control Module (ECM) sends a signal to each injector solenoid in order to provide complete control of the engine.Electronic Controls
The C-10, C-12, and C-15 Truck Engine's electronic system consists of the ECM, the engine sensors 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
RPM
Other characteristicsEngine Governor
The electronic controls that are on the engine serve as the engine governor.The electronic controls determine the timing 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.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 primary engine speed/timing sensor. 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 g00628869
(1) Accelerator pedal (2) Fuel injector (3) Primary engine speed/timing sensor (4) Engine Control Module (ECM)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
Intake manifold air temperature sensor
Atmospheric pressure sensor
Boost pressure sensorAt start-up, the ECM determines the top center position of the number 1 cylinder from the secondary engine speed/timing sensor's signal. After start-up, the ECM determines the top center position of the number 1 cylinder from the primary engine speed/timing sensor. The ECM decides 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 the best engine performance, the best fuel economy and the best control of white smoke. Actual timing cannot be viewed with the Caterpillar Electronic Technician (Cat ET), and desired timing cannot be viewed with Cat ET.
Illustration 2 g00628870
(1) Accelerator pedal (2) Fuel injector (3) Secondary engine speed/timing sensor (4) Primary engine speed/timing sensor (5) Engine Control Module (ECM)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