0387633 JOHNSON SPARK PLUG, Champion QL77J4

Recommended Actions
Diagnostic Codes
Use the electronic service tool to check for any diagnostic codes that may be related to high fuel consumption. 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 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 that is intended for use in high ambient temperatures will have a negative effect upon the rate of 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 oil is not of an acceptable quality or if the oil has exceeded the service life, drain the oil system and replace the oil filters. 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. These 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. This will require more fuel to be used.Air Inlet and Exhaust System
Leakage of gas or an increased restriction in either 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. Reduced Pressure of Intake Air
If the pressure of the intake air at the intake manifold is lower than normal, either the speed of the engine will need to be higher or more fuel must be injected in order to produce the same power. Either of these conditions will increase the fuel consumption. Note: If the engine is equipped with a wastegate regulator, low pressure in the air intake will create a 526-07 diagnostic code.
Check the pipe from the outlet of the turbocharger compressor to the intake manifold for leaks. If necessary, repair any leaks.
Check for the correct operation of the wastegate in the turbocharger. Refer to Systems Operation, Testing and Adjusting, "Turbocharger Wastegate - Test".
If the turbocharger is suspected as being faulty, replace the 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 the Troubleshooting Guide, "Excessive Valve Lash".Failure of the Primary Speed/Timing Sensor
If the primary speed/timing sensor fails, the engine will continue to operate using the signal from the secondary speed/timing sensor on the fuel rail pump. The secondary speed/timing sensor is less precise than the primary speed/timing sensor. Timing differences between the secondary speed/timing sensor and the primary speed/timing sensor may cause an increase in fuel consumption.
Use the electronic service tool to check for active diagnostic codes that relate to the primary speed/timing sensor.
If necessary, replace the primary speed/timing sensor. Refer to Disassembly and Assembly, "Speed/Timing Sensor - Remove and Install".