37978 Mercruiser SCREW, SWITCH AND SENDER TO GIMBAL RING (3/4")

Engine Speed/Timing Input Circuit
Engine speed is sensed by an electronic sensor. The same sensor is used for monitoring the position of the camshaft and engine speed . The speed/timing sensor has a self-adjusting pickup head. The signals are created as the timing reference ring rotates past the pickup (sliphead) of the engine speed/timing sensor. The timing reference ring is mounted on the rear of the left camshaft. A unique tooth pattern on the timing reference ring allows the ECM to determine the crankshaft position, the direction of rotation, and the speed. The ECM supplies the engine speed/timing sensor with 12.5 1.0 VDC which is required for proper operation.The output of the speed/timing sensor is a series of pulses. The frequency of the pulses is dependent upon the speed of the engine. The ECM interprets the frequency of the pulses as engine speed. The shape of the pulses is dependent upon the rotation position of the camshaft. The ECM reads the shape of the pulses in order to determine the position of the camshaft.Coolant Temperature Input Circuit
The temperature of the engine coolant is measured by an electronic sensor. The sensor is mounted on the cover of the regulator housing. The signal from the sensor is used to modify the fueling of the engine. The signal is also used to modify the timing for an improved cold start and reduction in white smoke. The ECM supplies the coolant temperature sensor with 5.0 0.5 VDC. The sensor's output voltage is 0.2 4.6 VDC. This depends on the temperature of the engine's coolant.Hydraulic Oil Temperature Input Circuit
Hydraulic oil temperature is measured by an electronic sensor that is mounted in the rear suction line near the hydraulic oil tank. The sensor signal is used to determine optimum fan speed for the hydraulic oil demand fan. The ECM supplies the hydraulic oil temperature sensor with 5.0 0.5 VDC. The sensor output voltage is 0.5 to 4.5 VDC. The ECM interprets the output voltage as hydraulic oil temperature.Throttle Switch Input Circuit
Desired engine speed is selected by the operator by using a ten position switch that is mounted in the cab area. The switch consists of four poles that connect to four switch inputs on the ECM through the vehicle wiring. Each pole is read as "grounded" or "open" by the ECM. The ECM compares the pattern of "grounded" or "open" switch poles to a preprogrammed table in memory in order to select the desired engine speed.Automatic Engine Speed Control (AESC)
The AESC switch allows the operator to enable the automatic engine speed control. The AESC system reduces engine speed to 1350 rpm when the operator has not moved a hydraulic control for four seconds. The AESC switch also acts as a backup for the throttle switch.User Defined Shutdown Circuit
The ECM reads this switch input. The ECM will terminate the fuel injection if the input is connected to the chassis ground. The shutdown is permanently recorded in the ECM as a logged event.Aftercooler Temperature Input Circuit
The aftercooler temperature sensor is located in the elbow for the aftercooler at the rear of the engine. The sensor receives a 13 volt supply voltage from the ECM. The sensor produces a 5000 Hz PWM signal. The signal's pulse width is interpreted by the ECM as aftercooler temperature.Gear Box Temperature Input Circuit
The gear box temperature sensor is located in the pump drive case at the rear of the engine. The sensor receives a 13 volt supply voltage from the ECM. The sensor produces a 5000 Hz PWM signal. The signal's pulse width is interpreted by the ECM as gear box oil temperature.Demand Control Fan System Output Circuit
The demand fan control provides a 0 to 1.8 amp signal to the solenoid valve that controls the oil flow to the fan drive motor. A 1.8 amp signal sets oil flow in the fan drive to minimum resulting in minimum fan speed. Conversely, a 0 amp signal sets oil flow in the fan drive to maximum resulting in maximum fan speed. The ECM reads the engine coolant temperature sensor in order to control the fan speed.Injector Output Circuits
An electrical signal from the ECM controls each electronic unit injector (EUI). This electrical signal determines the fuel injection timing. The duration of the electrical signal determines the quantity of fuel that is injected. The signal allows precise control of the injectors.Atmospheric Pressure Input Circuit
Atmospheric pressure is monitored by the atmospheric pressure sensor. The sensor is located on the mounting bracket for the ECM. A 5.0 0.5 VDC supply voltage is provided by the ECM. The output of the atmospheric pressure sensor is a DC signal. This signal has a range from 0.2 volts to 4.8 volts. The ECM interprets the output voltage as atmospheric pressure.Turbocharger Inlet Pressure Circuit
The air pressure in the air induction system for the engine is monitored by the turbocharger inlet pressure sensors. The sensors are located in each air inlet tube. The ECM provides the sensor with a 5.0 0.5 VDC supply voltage. The output of the turbocharger inlet pressure sensor is a DC voltage signal. The signal has a range from 0.2 volts to 4.8 volts. The ECM interprets the signal from this sensor as the inlet air pressure to the turbocharger compressors.Turbocharger Outlet Pressure Circuit
The engine's air inlet manifold pressure is monitored by the turbocharger outlet pressure sensor. The sensor is located at the front of the engine. The sensor is mounted in a block on the bracket of the front water regulator housing. The sensor receives a 5.0 0.5 VDC supply voltage from the ECM. The output of the sensor is a DC signal. The signal has a range from 0.2 volts to 4.8 volts. The signal is interpreted by the ECM as the absolute pressure of the inlet manifold.Elevated Low Idle Override
Under some ambient operating temperatures without increased engine speed, the machine will not reach the proper operating temperature after start-up. This is due to the cooling capacity of the machine.