859224 Mercury PLATE

Illustration 1 g02149628
Typical C18 Marine Engine which is cooled with a heat exchanger
(1) Engine coolant temperature sensor
(2) Engine coolant level sensor
(3) Fuel temperature sensor
(4) Control panel
(5) Inlet manifold air temperature sensor
(6) Inlet manifold air pressure sensor
(7) J1/P1 engine control module (ECM) connector
(8) J2/P2 ECM connector
(9) ECM
(10) Engine oil pressure sensor
(11) Fuel pressure sensor
(12) Timing calibration port
(13) Speed sensor (primary)
(14) Speed sensor (secondary) Failure of Sensors
All Sensors
One of the following malfunctions may cause a failure of a sensor:
Sensor output is open.
Sensor output is shorted to "- battery" or "+ battery".
Measured reading of the sensor is not within the specification.Coolant Temperature Sensor
The coolant temperature sensor monitors engine coolant temperature. The coolant temperature sensor is used by the engine system diagnostics with an output from the Electronic Control Module. The output of the ECM can indicate a high coolant temperature through a relay or a lamp. In addition, the sensor activates the cold start strategy which improves the startability of the engine.The minimum coolant temperature that will activate the alarm is 106°C (223°F). The switch opens as the coolant cools. A procedure for resetting is not required.Failure of the Coolant Temperature Sensor
If one of the following conditions exist, a failure of the coolant temperature sensor may have occurred:
Sensor output is open.
Sensor output is shorted to ground or supply.
Measured reading of the coolant temperature is out of the specification.The ECM will detect the failure of the coolant temperature sensor. The diagnostic lamp will warn the operator about the status of the coolant temperature sensor. Strategies that are related to the coolant temperature will be disabled if a failure occurs. The failure of the coolant temperature sensor will not cause a shutdown of the engine or any horsepower change.Coolant Level Sensor
The coolant level sensor monitors the engine coolant level. The sensor will detect coolant level. The coolant level sensor provides information to the ECM. The output from the ECM can indicate a low coolant level through a relay or a lamp. Coolant must be added to the cooling system in order to correct the condition. See the Operation and Maintenance Manual for more information.The system can be programmed with one of the following options:Enabled - The system will monitor the input from the coolant level sensor. The system is programmed with this value when the engine is shipped by Caterpillar.Disabled - The system will monitor the input from the coolant level sensor. All of the diagnostics that are associated with the coolant level sensor will be disabled.Failure of the Coolant Level Sensor
A failure of the coolant level sensor may occur under the following conditions:
The coolant level sensor is open.
The coolant level sensor is shorted to ground.
The coolant level sensor is shorted to supply.The failure of the coolant level sensor will not cause a shutdown of the engine or any horsepower change.Engine Oil Pressure Sensor
The engine oil pressure sensor can detect engine oil pressure for diagnostic purposes. The engine oil pressure sensor sends a signal to the Electronic Control Module (ECM).Low Oil Pressure Warning
The setpoint is dependent upon the engine rpm. The fault will be active and logged only if the engine has been running for more than 15 seconds. Very Low Oil Pressure Warning
The very low oil pressure setpoint is dependent upon the engine rpm. If Derate mode is selected, the ECM will derate the engine power. The engine horsepower will be limited.Failure of the Engine Oil Pressure Sensor
If one of the following conditions exist, a failure of the engine oil pressure sensor may have occurred:
The engine oil pressure sensor is open.
The engine oil pressure sensor is shorted to ground or supply.
Measured reading of the oil pressure is out of the specification.The ECM will detect the failure of the engine oil pressure sensor. The diagnostic lamp warns the user about the status of the engine oil pressure sensor. The oil pressure-related strategies will be disabled. The failure of the engine oil pressure sensor will not cause a shutdown of the engine or any horsepower change.Fuel Pressure Sensor
The fuel pressure sensor monitors the fuel filter pressure. Low fuel pressure or high fuel pressure will not cause a shutdown of the engine or any horsepower change. Fuel pressure that is outside of the normal range will affect the engine performance. If the fuel filter outlet pressure is low, the fuel filter may need to be replaced.
Table 1
Fuel Pressure Sensor
Minimum allowable pressure of the fuel transfer pump at full load speed 415 kPa (60 psi)
Minimum allowable pressure in the fuel manifold at full load speed 276 kPa (40 psi) Fuel Temperature Sensor
The fuel temperature sensor monitors the fuel temperature. Fuel temperature is monitored in order to adjust the fuel rate so that the engine will deliver consistent power. The fuel temperature sensor can also be used to warn the operator of excessive fuel temperature. A high fuel temperature can adversely affect the engine performance.
Table 2
Fuel Temperature Sensor
Operating range of the fuel temperature sensor for activation of the power correction by the ECM 30 to 70°C (86 to 158°F) Air Temperature Sensor for the Inlet Manifold
The air temperature sensor for the inlet manifold measures the inlet manifold air temperature. The Electronic Control Module (ECM) monitors the signal from the air temperature sensor for the inlet manifold. The output of the ECM can indicate high inlet manifold air temperature through a relay or a lamp. The air temperature sensor for the inlet manifold will not cause a shutdown of the engine or any horsepower change.Note: Heat from the inlet manifold may affect the temperature sensor for the inlet manifold. This sensor may be affected when the engine is idling and after the engine is shut off. This warm-up is due to the lack of coolant circulation through the engine and will exist until the air inside the inlet manifold cools.Air Pressure Sensor for the Inlet Manifold
The air/fuel ratio control utilizes actual engine speed and actual boost pressure (inlet manifold air pressure) in order to control the transient smoke level. When the throttle is increased and