955542 Volvo.Penta Hexagon screw

Electronic Controls
Electronic Control Module
The ECM consists of two main components, the control computer (hardware) and the personality module (flash file). The control computer consists of a microprocessor and electronic circuitry. The personality module is the software for the control computer. The personality module also stores operating maps that define power and torque curves. The ECM determines the engine's operating conditions through feedback from engine sensors. The ECM controls the engine by limiting the duration of fuel injection.Engine Governor
The engine ECM governs engine speed. The engine ECM and the personality module work together by controlling the amount of fuel that is delivered by the fuel injectors. Desired engine rpm is determined by the throttle position sensor signal and by certain sensor readings. Actual engine rpm is measured by the engine speed/timing signal.Fuel Injection
The engine ECM controls the timing and the duration of fuel injection. The engine ECM varies the signals to the fuel injectors. Fuel is injected only while an injector solenoid is energized by a 105 volt signal from the engine ECM. By controlling the timing and duration of the 105 volt signal, the ECM can control the engine speed.Injection timing is dependent on the engine speed and on the engine load. The ECM can detect the top center of the number one cylinder from the engine speed/timing signal. The ECM decides when injection should occur relative to top center of the number one cylinder. The ECM sends an injection signal at the desired time.Fuel Ratio Control Limit (FRC)
The flash file inside the engine ECM sets certain limits on the amount of fuel that can be injected. The FRC Limit is used to control the air/fuel ratio for control of emissions. The FRC is a limit that is based on the boost pressure. The boost pressure is calculated as the difference in pressure between atmospheric pressure and turbocharger outlet pressure. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC. When the engine ECM increases the FRC, the engine ECM allows more fuel into the cylinder.Rated Fuel Position
The rated fuel position is a limit that is based on the power rating of the engine. The rated fuel position is similar to the rack stops and to the torque spring on a mechanically governed engine. The rated fuel position determines maximum power and torque values for a specific engine family and for a specific rating. The rated fuel position is programmed into the flash file of the personality module at the factory.Note: These limits are programmed by the factory into the personality module. These limits are not programmable in the field.Cold Mode Operation
The engine ECM uses cold mode operation in order to reduce white smoke during engine warm-up. The engine ECM cuts out the injectors one at a time in order to determine if the cylinder is firing. If the cylinder is firing correctly, the engine ECM leaves the injector on. If the cylinder is not firing, the engine ECM will leave the injector off. This will increase startability and this will reduce warm up time.Cold Mode is activated whenever the engine coolant temperature falls below a predetermined value. Cold Mode remains active until the engine has warmed or a time limit is exceeded.Block Diagram of Electronic Governor
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Electronic System Component Diagram
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Electronic System Component Diagram
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Location of the 3512 Engine Sensors on the 784B and 785B OHT
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Right side view (1) Right turbocharger inlet pressure sensor (2) Oil pressure sensor (3) ECM connector J1/P1 (4) Electronic Control Module (ECM) (5) Brake solenoid for the fan (6) Coolant flow switch (7) Timing calibration connector
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Left side view (8) Coolant temperature sensor (9) Sender for coolant temperature (10) Machine interface connector P2 (11) Ether enable temperature switch (12) Turbocharger outlet pressure sensor (13) Remote shutdown switch (14) Fuel filter differential pressure sensor (15) ECM ground bolt (16) Switch for torque converter
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Front and rear view (1) Right turbocharger inlet pressure sensor (2) Oil pressure sensor (4) Electronic Control Module (ECM) (6) Coolant flow switch (7) Timing calibration connector (8) Coolant temperature sensor (10) Machine interface connector P2 (12) Turbocharger outlet pressure sensor (17) Fan control solenoid (18) Left turbocharger inlet pressure sensor (19) Fan speed sensor (20) Engine speed/timing sensor (21) Magnetic tachometer sensorLocation of the 3516 Engine Sensors on the 789B and 793B OHT