SEAL KIT- 9X2644 - Caterpillar

System Operation
The 3176B Engines were designed for electronic control. The injection pump, fuel lines and nozzles used in traditional Caterpillar engines have been replaced with an electronic unit injector in each cylinder. A solenoid on each injector controls the amount of fuel delivered by the injector. An Electronic Control Module (ECM) sends a signal to each injector solenoid to provide complete fuel injection control.Electronic Controls
The 3176B electronic system consists of two components, the Electronic Control Module (ECM) and the Personality Module, and various sensors. The ECM is the computer which controls the 3176B engine. The Personality Module contains the software which controls how the ECM behaves (stores the operating maps that define power, torque curves, rpm, etc). Early machines have a separate Personality Module component. Later machines have the Personality Module integral to the ECM. For information, refer to Programming Parameters section in this manual.The ECM determines a "desired rpm" based on the throttle input signal and certain diagnostic codes. The ECM then maintains the desired engine rpm by sensing actual engine rpm and deciding how much fuel to inject in order to achieve the desired rpm.Fuel Injection
The ECM controls the amount of fuel injected by varying signals to the injectors. The injectors will inject fuel ONLY if the injector solenoid is energized. The ECM sends a high voltage signal to the solenoid to energize it. 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 sets certain limits on the amount of fuel that can be injected. "FRC Fuel Pos" is a limit based on boost pressure to control the fuel-air ratio, for emissions control purposes. When the ECM senses a higher boost 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 horsepower rating of the engine. It is similar to the rack stops and torque spring on a mechanically governed engine. It provides horsepower and torque curves for a specific engine family and rating. All of these limits are programmed at the factory into the Personality Module and are not programmable in the field.Injection timing depends on engine rpm, load and other operating factors. The ECM knows where top-center on cylinder number one is from the signal provided by the engine Speed/Timing Sensor. It decides when injection should occur relative to top-center and provides the signal to the injector at the desired time.Fuel Temperature Monitoring
The Fuel Temperature Sensor monitors the fuel temperature and adjusts the ECM calculated fuel rate to compensate for fuel temperature changes.For fuel temperatures above 30°C (86°F) the ECM will adjust the rated fuel position to provide constant power.Altitude Derate
This feature protects the engine at altitudes above 2286 meters (7500 feet) by using the atmospheric pressure sensor input (less than 67 kPa [9.7 psi]) to the ECM. The ECM will adjust engine operating parameters to reduce engine rpm and power.Lifetime Operating Data