0209942 JOHNSON PLATE, Applique, front, 20

Fuel System (Air/Fuel Ratio Control)
The fuel system includes these components:
Catalyst thermocouple sensor
Engine control module (ECM)
Fuel actuator and valve
Inlet manifold pressure sensor
Oxygen sensor and buffersThe fuel metering valve controls the flow of fuel to the engine. The ECM determines the requirement for the mixture of air and fuel. The ECM sends a signal to the fuel metering valve. The fuel metering valve controls the volume of the gas flow to the engine.The oxygen sensor measures the oxygen content in the exhaust gas. The inlet manifold pressure and engine speed are monitored. This information is provided to the ECM. The ECM uses this information to adjust the flow of fuel to meet emissions requirements. This action is a continuous process during engine operation.The fuel flows through the fuel metering valve into the carburetor. Air flows into the carburetor and is mixed with fuel. The air/fuel mixture enters the cylinders through a throttle valve. On turbocharged engines (if equipped), air is compressed and flows into the carburetor, where the air is mixed with fuel. The air/fuel mixture flows through the throttle valve and is cooled using the aftercooler before entering the cylinder.The ECM sends a signal to the throttle valve. The throttle controls the flow of the air/fuel mixture to the cylinders.Ignition System
The engine is equipped with an A4-E2 ignition system. The system is controlled by the ECM, and provides dependable firing and low maintenance. The system provides precise control of the spark and the ignition timing for each cylinder. The system also provides diagnostic capability that enhances troubleshooting.The ignition system has four basic components: an air fuel ratio control system (AFRC) controlled by the electronic control module (ECM), an ignition transformer for each cylinder, wiring harness, and spark plugs.Lubrication System
The engine lubrication oil is circulated by a gear-driven pump. The oil is cooled and the oil is filtered. However, bypass valves provide an unrestricted flow of lubrication oil to the engine if the following conditions occur:
The viscosity of the oil is high because the oil is cold.
The oil cooler becomes plugged.
The oil filter becomes plugged.Cooling System
The jacket water coolant is circulated by a gear-driven centrifugal pump. A 90 °C (194 °F) temperature regulator regulates the temperature of the coolant. Heat can be removed from the coolant by a radiator or a heat exchanger.For engines with a Separate Circuit Aftercooler (SCAC), the air is cooled by a heat exchanger. The water that cools the air in the heat exchanger is in a circuit that is separate from the jacket water. The aftercooler coolant is pumped by an auxiliary water pump. The SCAC is required to operate at one of the following temperatures. The engine rating depends on the temperature and the application.
32 °C (90 °F)
54 °C (129 °F)For engines with air-to-air aftercooling, the aftercooler is supplied by the customer. This aftercooler is similar to a radiator. The inlet air is cooled by a fan that moves the ambient air through the radiator.Engine Service Life
Engine efficiency and maximum utilization of engine performance depend on adherence to proper operation and maintenance recommendations. These recommendations include the use of recommended lubricants, fuels, and coolants.For the engine maintenance that is required, refer to the Operation and Maintenance Manual, "Maintenance Interval Schedule" (Maintenance Section).