809981 Mercruiser SCREW-Drain (12MM)

Electronic Controls
Electronic Control Module
The ECM supplies signals to the Electronic Fuel Injectors. The ECM signals control the engine operation. The ECM consists of the following components: control computer (hardware) and Personality Module (software). The control computer consists of a microprocessor and electronic circuitry. The Personality Module is the software for the control computer which contains operating maps that define power and torque curves.The ECM governs engine speed. The ECM and the Personality Module work together by controlling the amount of fuel that is delivered by the injectors. Desired engine rpm is determined by the throttle position sensor signal and certain sensor readings. Diagnostic codes may derate the engine. Actual engine rpm is determined by the Engine Speed/Timing signal.Fuel Injection
The ECM controls the timing of the fuel injectors. 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 fuel injection timing, the quantity of fuel and the desired engine rpm.Injection timing depends on the following conditions: engine rpm and load other operational factors. The ECM detects the top center of each cylinder. The ECM sends an injection signal at the desired time. The ECM limits engine power during cold mode operation. The ECM modifies the injection timing and the ECM cuts out the cylinders. 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.The ECM is programmed at the factory which limits the quantity of fuel that can be injected. The FRC Fuel Position controls the fuel limit for exhaust smoke. The FRC is based on the maximum allowable fuel to air ratio. The FRC Fuel Position is increased when the ECM senses a higher Turbocharger Compressor Outlet Pressure. This will allow more fuel into the cylinder.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 provides power. The Rated Fuel Position provides the power curves and the torque curves for a specific engine family.Block Diagram of Electronic Governor
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Engine Wiring Diagram
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Engine Wiring Diagram
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Location of the 3508B Engine Components
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Rear view (1) Aftercooler temperature sensor (2) Machine interface connectors (3) Engine speed/timing sensor (4) Starting motorsLocation of the 3508B Engine Components
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Front view (5) Right turbocharger inlet compressor pressure sensor (6) Left turbocharger inlet compressor pressure sensor (7) Atmospheric pressure sensor (8) Turbocharger compressor outlet pressure sensor (9) ECM connector J2/P2 (10) Alternator (11) ECM connector J1/P1 (12) Electronic control module(ECM) (13) Extremely low oil level switchLocation of the 3508B Engine Components
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Left side view (14) Coolant temperature sensor (15) Left exhaust temperature sensor (16) Fuel filter differential pressure switch (17) Crankcase pressure sensor (18) Ground boltLocation of the 3508B Engine Components
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Right side view (19) Right exhaust temperature sensor (20) Engine shutdown switch (21) Unfiltered engine oil pressure sensor (22) Filtered engine oil pressure sensor (23) Coolant flow switch (24) Timing calibration plugLocation of the 3516B Engine Components
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Rear view (1) Aftercooler temperature sensor (2) Fuel filter differential pressure switch (3) Machine interface connectors (4) Engine speed/timing sensorLocation of the 3516B Engine Components