TANK 4N6649 - Caterpillar

System Operation
Illustration 1 g01808033
(1) Electronic Unit Injector (2) Solenoid for the Fuel Rail Pump (3) Wastegate Regulator (if equipped) (4) Secondary Speed/Timing Sensor (5) Fuel Rail Pump (6) Primary Speed/Timing Sensor (7) Intake Manifold Pressure Sensor (8) Fuel Rail Pressure Sensor (9) Engine Oil Pressure Sensor (10) Intake Manifold Temperature Sensor (11) Coolant Temperature Sensor (12) Diagnostic Connector (if equipped) (13) Electronic Control Module (ECM)The C6.6 engine was designed for electronic control. The engine has an Electronic Control Module (ECM), a fuel rail pump and electronic unit injectors. All of these items are electronically controlled. There are also a number of engine sensors. Turbocharged engines can be equipped with an electronically controlled wastegate for the turbocharger. The ECM controls the engine operating parameters through the software within the ECM and the inputs from the various sensors. The software contains parameters that control the engine operation. The parameters include all of the operating maps and customer selected parameters.The electronic system consists of the ECM, the engine sensors and inputs from the parent machine. The ECM is the computer. The personality module is the software for the computer. The personality module defines the following characteristics of the engine:
Engine power
Torque curves
Engine speed (rpm)
Engine Noise
Smoke and EmissionsEngine Speed Governor
The ECM determines the injection timing, the amount of fuel that is delivered to the cylinders and the intake manifold pressure if an electronically controlled wastegate is installed on the turbocharger. These decisions are based on the actual conditions and the desired conditions at any given time.The governor has software that compares the desired engine speed to the actual engine speed. The actual engine speed is determined through the primary speed/timing sensor and 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.Timing Considerations
Fuel injection timing is determined by the ECM after considering 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
Speed demand deviceAt start-up, the ECM determines the top center position of the number 1 cylinder from the secondary speed/timing sensor in the fuel rail pump. The ECM decides 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 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 the best engine performance, the best fuel economy and the best control of