346-00001-1 Tohatsu PISTON (STANDARD)

Illustration 1 g00764826
(1) Secondary speed/timing sensor
(2) Inlet manifold boost pressure sensor
(3) Customer connector
(4) Electronics ground stud
(5) Fuel pressure sensor
(6) Fuel temperature sensor
(7) Inlet manifold temperature sensor
(8) TDC probe connector
(9) Electronic control module (ECM)
(10) Engine oil pressure sensor
(11) Atmospheric pressure sensor
(12) Primary speed/timing sensor Coolant Temperature Sensor
Illustration 2 g00764853
Location of the coolant temperature sensor
The engine coolant temperature sensor monitors the temperature of the engine coolant. The coolant temperature signal is sent to the Electronic Control Module (ECM) for engine monitoring and for improved engine control. The signal is used by the ECM for all of the following engine functions:
Engine timing control
Engine operating mode
Engine protectionThe ECM is capable of adjusting the engine timing relative to the engine operating temperature. The concept of dynamic timing provides the engine with the ability to control exhaust emissions. Timing control also aids in white smoke cleanup during cold engine operation.The ECM also uses the signal from the engine coolant temperature sensor to determine the mode of operation for the engine. Several aspects of engine operation are affected by the engine operating mode: acceleration ramp rates, engine timing and fuel injector timingHigh Coolant Temperature Warning
Excessive engine coolant temperature is an undesirable operating condition. Serious damage to the engine can result if an engine is allowed to overheat. The "High Engine Coolant Temperature" parameter for the programmable monitoring system must be programmed to "Derate" or "Shutdown" in order to protect the engine against damage from overheating.Coolant Level Sensor
Illustration 3 g00761897
Typical example
Location of the coolant level sensor
The coolant level sensor is an optional sensor. This sensor monitors the engine coolant level in the cooling system expansion tank. The coolant level sensor signal is sent to the ECM for the purpose of engine monitoring. Low Coolant Level Warning
Low engine coolant level is an undesirable operating condition. Serious damage to the engine can result if the coolant level is too low and the engine is allowed to overheat. The "Low Coolant Level" parameter for the programmable monitoring system must be programmed to "Derate" or "Shutdown" in order to protect the engine against damage from a low coolant level.Engine Oil Pressure Sensor
Illustration 4 g00764686
Location of the engine oil pressure sensor
The engine oil pressure sensor provides an oil pressure signal to the Electronic Control Module (ECM) for the purpose of engine monitoring. The electronic signal is compared to an Oil Pressure Map that is stored in ECM memory. The Oil Pressure Map is derived from a direct relationship between engine speed and the oil pressure that is expected at that speed. The engine monitoring system records a low engine oil pressure condition in ECM memory if the sensor value is not within the proper range.Low Oil Pressure Warning
Low engine oil pressure is an undesirable operating condition. When a low oil pressure condition exists in the engine, there is a possibility of damage to major engine components. The "Low Engine Oil Pressure" parameter for the programmable monitoring system must be programmed to "Derate" or "Shutdown" in order to protect the engine against damage from low engine oil pressure.Fuel Temperature Sensor
Illustration 5 g00764773
Location of the fuel temperature sensor
The fuel temperature sensor monitors the inlet fuel temperature. The Electronic Control Module (ECM) utilizes the signal from the fuel temperature sensor to provide fuel temperature compensation for the engine fuel control system. Fuel temperature compensation provides the following benefits:
Rated engine horsepower regardless of fuel temperature
Highly accurate fuel rates and fuel consumption rates
Optimum fuel economyChanges in the temperature of the fuel affects the power output of the engine. The ECM adjusts the engine fuel rate according to the temperature of the fuel. This feature allows full engine power to be realized by the operator at any fuel temperature.Fuel temperature will also affect the calculation of fuel consumption rate that is performed by the ECM. The ECM utilizes the fuel temperature signal to provide an adjusted value for these calculations.High Fuel Temperature Warning
High fuel temperature is an undesirable operating condition. The "High Fuel Temperature" parameter for the programmable monitoring system must be programmed to "Derate" or "Shutdown" in order to protect the engine.Fuel Pressure Sensor
Illustration 6 g00764778
Location of fuel pressure sensor
The fuel pressure sensor monitors filtered fuel pressure. Although fuel pressures that are outside the normal operating range may adversely affect engine performance, there should not be any noticeable reduction in the engine horsepower. Abnormal fuel pressure will not cause an engine shutdown. A low filtered fuel pressure may indicate that the low pressure fuel system requires maintenance. The fuel pressure sensor measures the fuel pressure after the fuel has been filtered. The sensor connector for the fuel pressure sending unit is located on the machine side of the machine connector. For more information, refer to the Troubleshooting Guide for this engine.For more information on fuel system maintenance, refer to the maintenance section in this Operation and Maintenance Manual.