14474 Mercruiser FUEL LINE

System Overview
The 3176C Engine is designed for electronic control. The electronic system consists of an Electronic Control Module (ECM), Electronic Unit Injectors (EUI), wire harness, switches, and sensors (refer to Figures 1.1, 1.2, & 1.3). A solenoid on each injector controls the amount of fuel delivered by the injector. The Electronic Control Module (ECM) monitors each sensor and provides the signal (power) to each injector solenoid to provide complete control of the engine.Electronic Controls
The Electronic Control Modules consist of two main components, the control computer (hardware) and the Personality Module (software). The control computer is the microprocessors and electronic circuitry. The Personality Module contains the software for the control computer which stores operating maps that define power and torque curves. The two work together to control engine operation.The ECM determines a desired engine speed based on the throttle selection and other sensor input signals and certain diagnostic codes. The ECM maintains the desired engine speed by sensing actual engine speed using the Speed/Timing Sensor, then determines how much fuel to inject in order to achieve the desired engine speed. Some operating conditions (cold mode, derates, diagnostic codes and events) will alter engine speed from the desired engine speed.Fuel Injection
The ECM controls the timing and quantity of fuel injected by varying the signals to the injectors. The injectors will inject fuel ONLY when the injector solenoids are energized by a 105 VDC signal supplied by the ECM. By controlling the timing and duration of the 105 VDC signal, the ECM can control injection timing and the amount of fuel injected based on engine rpm, load, and other operating conditions.The ECM limits engine power and modifies injection timing during COLD MODE operation (when enabled) to increase startability, reduce warm-up time, and reduce white smoke. During COLD MODE operation, the ECM will automatically disable fuel injection to non-firing cylinders until the engine temperature increases. COLD MODE may be activated whenever the engine temperature falls below a predetermined value and remains active until the engine temperature rises above a predetermined value or a time limit is exceeded.The ECM has factory programmed limits on the amount of fuel that can be injected. FRC Fuel Pos is a fuel limit for exhaust smoke control purposes that is based on the maximum allowable fuel-to-air ratio. When the ECM senses a higher Turbocharger Compressor Outlet Pressure (more air available), the FRC Fuel Pos limit is increased to allow more fuel into the cylinder. Rated Fuel Pos is a limit based on the power rating of the engine. It is similar to the rack stops and the torque spring on a mechanically governed engine. The Rated Fuel Pos provides power and torque curves for a specific engine family and rating.The two limits (FRC Fuel Pos and Rated Fuel Pos) are programmed by 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 (TC) of every cylinder is from the signal provided by the engine Speed/Timing Sensor. The ECM decides when injection should occur relative to the piston top center position and provides a signal to the injector at the desired time.Programmable Parameters
System Configuration Parameters are parameters stored in the ECM that affect engine operation. The parameters are set at the factory and may be changed with an Electronic Service Tool ( ET - Electronic Technician or ECAP - Electronic Control Analyzer Programmer). However, a factory password may be required to change certain parameters.Self-Diagnostics
The Electronic Control Module has some ability to diagnose itself. When a problem is detected, a diagnostic code is generated and a visible alarm will be present at the Check Engine Lamp. The diagnostic code is also stored in the ECM's permanent memory.Current diagnostic codes are referred to as ACTIVE. An Active code indicates a problem currently exists. They should always be serviced first. Refer to Section 4: Troubleshooting With A Diagnostic Code for more information.Diagnostic codes stored in memory are called LOGGED. The problem may have been temporary or may have been repaired since the time it was logged. It is important to remember that it is possible to log faults whenever a component is disconnected and the keyswitch is in the ON position. Therefore, logged diagnostic codes do not necessarily mean something needs to be repaired. Logged diagnostic codes may be helpful indicators to determine intermittent problems.In addition to diagnostic codes, the ECM also records EVENTS (such as high coolant temperature or low oil pressure) that have occurred, rather than diagnostics or electronic problems. Refer to Section 4: Troubleshooting With a Diagnostic Code for more information on Event Codes.Passwords
Several System Configuration Parameters and most Logged Events are protected by Factory Passwords. Factory passwords are calculated on a computer and are available only to Caterpillar dealers. Refer to Programming Parameters in Section 2 for details regarding when passwords are needed and how to obtain them.Electronic Governor
Figure 1.1 - 3176C Electronic Governor Diagram for 480/485 Lexion CombineBasic Engine Block Diagram
Figure 1.2 - 3176C Engine Block Diagram for 480/485 Lexion CombineSensor and Connector Locations
Figure 1.3 - Sensor and Connector LocationsElectronic Service Tools
The Caterpillar Electronic Service Tools are designed to help the service technician obtain and analyze data, and diagnose existing and potential problems within the electronic system. Their use is required to perform calibrations and to read or change programmable parameters.There are two Caterpillar Electronic Service Tools that can be used to service the 3176C Combine Engine; Electronic Technician (ET) and Electronic Control Analyzer Programmer (ECAP). With either ET or ECAP, a Communication Adapter Tool is required to communicate with the Electronic Control Module. ET is the preferred Electronic Service Tool due to its increased functionality, however, the ECAP may be used to perform basic troubleshooting procedures.The digital multimeter is suitable for making voltage and resistance measurements. There are also several adapter cables, probes, etc, that allow the service technician to perform the measurements and obtain readings needed for diagnosis. These tools are