8M0005773 Mariner SCREW, (M6)

Engine Speed Governor
The governor has software that compares the desired engine speed to the actual engine speed. The actual engine speed is determined through a signal from the primary speed/timing sensor and from the secondary 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. If the actual engine speed is greater than the desired engine speed, the governor limits the amount of fuel that is supplied to the electronic unit injectors in order to reduce engine speed.Timing Considerations
Fuel injection timing is determined by the ECM after analyzing input from the following components:
Engine coolant temperature sensor
The sensor for the intake manifold air temperature
The sensor for the intake manifold pressure
Speed/timing sensors
Throttle position sensorAt engine start-up, the ECM determines the top center position of the number one cylinder from the speed/timing sensors' signal. The ECM determines when fuel injection should occur relative to the top center position. The ECM optimizes engine performance by control of each of the electronic unit injectors so that the required amount of fuel is injected at the precise point of the engine's cycle. The electronic unit injectors are supplied with high pressure fuel from the fuel rail. The ECM also provides the signal to the solenoid in the fuel rail pump. The solenoid in the fuel rail pump controls a valve in the fuel rail pump. This valve controls the pressure in the fuel rail. Fuel that is not required for the engine is diverted away from the fuel rail pump back to the fuel tank.The ECM adjusts injection timing and fuel pressure for optimum engine performance, fuel economy and control of exhaust emissions.Fuel Injection
The flash file inside the ECM sets certain limits on the amount of fuel that can be injected.The Fuel Ratio Control (FRC) limit is based on intake manifold pressure and on engine rpm. The FRC limit is used to control the air/fuel ratio in order to control the engine's exhaust emissions. When the ECM senses a higher intake manifold pressure, the ECM increases the FRC limit. A higher intake manifold pressure indicates that there is more air in the cylinder. When the ECM increases the FRC 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 on the engine rpm. The rated fuel limit enables the engine power and torque outputs to conform to the power and torque curves of a specific engine model.Programmable Parameters
System configuration parameters can affect the power rating or the emissions of the engine and may be changed with electronic service tools. Examples of these parameters are Full Load Setting (FLS) and Full Torque Setting (FTS). The parameters are stored in the ECM and factory passwords must be obtained in order to change some of the system configuration parameters. Factory passwords are calculated on a computer system that is available only to Caterpillar distributors.Refer to Troubleshooting, "Configuration Parameters" and Troubleshooting, "Factory Passwords".