21085 Mercruiser STUD, (#10-32 x .930)

Electronic Controls
Electronic Control Module
The ECM controls the engine operation. The ECM supplies signals to the electronic unit injectors (EUI). The ECM consists of the following components: control computer (hardware) and Software. The control computer consists of a microprocessor and of electronic circuitry. The software contains operating maps that define power and torque curves.The ECM governs engine speed. Desired engine rpm is determined by the throttle signal and by certain sensor readings. Diagnostic codes may derate the engine. Actual engine rpm is determined by the engine speed/timing sensor.Fuel Injection
The ECM detects the top center of the number one cylinder from the timing pulse of the engine speed/timing sensor. The ECM controls the timing and duration of the fuel injection. The 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 ECM. By controlling the timing and duration of the 105 volt signal, the ECM controls the engine rpm. Injection Timing depends on engine rpm and load.Cold Mode Operation
The ECM limits engine power during Cold mode operation. Cold mode operation is activated whenever the engine coolant temperature falls below a predetermined value. Cold mode operation remains active until the engine has warmed or until a preset time limit is exceeded.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.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 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. The FRC is used to control the air/fuel ratio for control of emissions. When the engine ECM senses a higher boost pressure, the engine ECM increases the FRC. A higher boost pressure indicates that there is more air in the cylinder. 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 engine power rating. This is similar to the rack stops and the torque spring on a mechanically governed engine. The rated fuel position determines the 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.Engine Wiring Diagram (9TR and 9XR)
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Engine Wiring Diagram (9TR and 9XR)
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Engine Wiring Diagram (AAF and 7PZ)
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Engine Wiring Diagram (AAF and 7PZ)
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Location Of The 3508B Engine Sensors (9TR and 9XR)
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Left side view 3508B (1) Coolant temperature sensor (2) Turbocharger compressor outlet pressure sensor (3) Engine oil pressure sensor (4) Left hand exhaust temperature sensor (5) Engine speed/timing sensor (6) Crankcase pressure sensor (7) Ground (8) Ground stud for the ECM (9) Starting motors (10) Ground (11) Connectors for the start relays (12) Data link connector (13) Connector for the alternator circuit breaker (14) Machine interface connectorLocation Of The 3508B Engine Sensors (9TR and 9XR)
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Right side view 3508B (15) Fuel filter differential pressure switch (16) Right hand exhaust temperature sensor (17) Atmospheric pressure sensor (18) Connector for the crank without injection (19) Permanent timing calibration sensor (20) Engine oil level sensor (21) Coolant flow switch (22) ECMLocation Of The 3508B Engine Sensors (9TR and 9XR)
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Front view 3508B (18) Connector for the crank without injection (22) ECM (23) Turbocharger compressor inlet pressure sensorLocation Of The 3508B Engine Sensors (9TR and 9XR)