804153 Mercury KEY

Recommended Actions
Diagnostic Codes
Use one of the following methods to check for active diagnostic codes:
The electronic service tool
The display on the control panelElectronic Service Tool
Connect the electronic service tool to the diagnostic connector.
Check for active diagnostic codes on the electronic service tool.
Investigate any active codes before continuing with this procedure. Refer to Troubleshooting, "Troubleshooting with a Diagnostic Code". Display on the Control PanelNote: The following procedure is only applicable if the application is equipped with a display on the control panel.
Check the display on the control panel for active diagnostic codes.
Troubleshoot any active codes before continuing with this procedure. Refer to Troubleshooting, "Troubleshooting with a Diagnostic Code". Misreading of Fuel Level
Monitor the fuel consumption over a period of 50 engine hours. If the fuel consumption is excessive, perform the following procedure. Fuel Leakage
Check for evidence of fuel leaks on the engine. Rectify any leaks. Fuel Quality
The quality of the fuel that is used in the engine will affect the rate of fuel consumption. Refer to "General Fuel Information" in the Operation and Maintenance Manual, "Refill Capacities".
If the fuel is not of an acceptable quality, drain the fuel system and replace the fuel filters. Refill the fuel system with fuel of an acceptable quality. Refer to the applicable sections in the Operation and Maintenance Manual.
If the fuel is of an acceptable quality, refer to "Quality of Oil". Quality of Oil
The nominal viscosity of the lubricating oil that is used in the engine will affect the rate of fuel consumption. The viscosity of lubricating oil is defined by the SAE grade of the lubricating oil. The grade of the lubricating oil must be correct for the ambient conditions. Lubricating oil for high ambient temperatures will affect fuel consumption in cold ambient temperatures. Refer to "Engine Oil" in the Operation and Maintenance Manual, "Refill Capacities".
The actual viscosity of the lubricating oil that is used in the engine will change throughout the service life of the oil. Lubricating oil that is heavily contaminated will have a negative effect upon the rate of fuel consumption.
If the quality of the oil is unacceptable or the oil has exceeded the service life, drain the oil system and replace the oil filter. Refill the oil system with oil of an acceptable quality. Refer to the applicable sections in the Operation and Maintenance Manual.
If the oil is of an acceptable quality, refer to "Low Engine Temperature". Low Engine Temperature
The operating temperature of the engine will affect the rate of fuel consumption. Operation of the engine below the correct temperature will increase fuel consumption. Failure of the water temperature regulator can prevent the engine from operating at the correct temperature.
If the engine operating temperature is low, check the operation of the water temperature regulator. If the water temperature regulator does not operate correctly, a new water temperature regulator must be installed. Refer to Disassembly and Assembly, "Water Temperature Regulator - Remove and Install". Prolonged Operation at Idle Speed
Prolonged operation of the engine at idle speed increases fuel consumption. When the engine is operated at idle speed, the fuel that is consumed provides no useful work. Prolonged operation at idle speed will cause a measurable deterioration in the overall fuel consumption of the engine.Operation of the engine for long periods at idle speed will cause a deterioration of the internal components of the engine. A deterioration of the internal components of the engine will increase fuel consumption.Engine Operating Speed
The operating speed of the engine will affect the rate of fuel consumption.High engine speed will increase fuel consumption. At high engine speeds, internal power losses in the engine increase and more power is required to drive the alternator and the fan. The power losses increase fuel consumption. Lugging down the engine to a low engine speed will increase fuel consumption. At low engine speeds, the combustion efficiency of the engine is reduced and more fuel will be used.Air Inlet and Exhaust System
Leakage of gas or a restriction in the air intake or the exhaust system can reduce the flow of combustion gas through the engine. A change in the flow of combustion air into the engine adversely affects combustion efficiency and the rate of fuel consumption.
Check the air intake system for leakage or restrictions. Refer to Systems Operation, Testing, and Adjusting, "Air Inlet and Exhaust System".
Check the exhaust system for leakage or restrictions. Refer to Systems Operation, Testing, and Adjusting, "Air Inlet and Exhaust System".
Repair all defects. Verify that the repair has eliminated the fault. Aftertreatment Regeneration Device (ARD)
If the ARD is operating more frequently than normal, fuel consumption can increase. Investigate the cause of the frequent operation of the ARD.Cooling Fan
Damage to the cooling fan will increase fuel consumption. Check the cooling fan for damage and repair, if necessary.Reduced Pressure of Intake Air
If intake manifold pressure is low, the engine speed will need to be higher or more fuel must be injected to produce the same power. Either of these conditions will increase the fuel consumption.
Check all pipes from the outlet of the turbocharger compressor (if equipped) to the inlet manifold for leaks. If necessary, repair any leaks.
If equipped, check for the correct operation of the wastegate in the turbocharger. Refer to Systems Operation, Testing, and Adjusting, "Turbocharger - Inspect".
If equipped, replace a faulty turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install". Excessive Valve Lash
Excessive valve lash will cause a change in the timing of the opening and closing of the inlet and exhaust valves. Excessive valve lash can cause a reduction of the flow of combustion air into the engine. Reduced flow of combustion air will increase the fuel consumption rate.Refer to Troubleshooting, "Valve Lash Is Excessive".Failure of the Primary Speed Sensor
If the primary speed sensor fails, the engine will continue to operate using the signal from the secondary speed sensor. The secondary speed sensor is less precise than the primary speed sensor. Timing differences between the secondary speed sensor and the primary speed sensor may cause an increase in fuel