K 2500 Truck 4WD V8-350 5.7L VIN K TBI (1995)
EGR Valve: Description and Operation
Port EGR Valve
EGR Valve
PURPOSE:
The EGR system routes exhaust gases from the exhaust manifold to the intake manifold at specified engine operating conditions. The EGR valve is
opened by vacuum to let exhaust gas flow into the intake manifold. The exhaust gas then moves with the air/fuel mixture into the combustion
chamber. Since there is less air/fuel mixture to burn in the combustion chamber during EGR operation, the temperature is reduced enough to limit
NOx formation. If too much exhaust gas enters, combustion will NOT occur. Because of this, very little exhaust gas is allowed to pass through the
valve, especially at idle. The valve should only open when the engine is at operating temperature and above idle speed. The EGR vacuum control
solenoid and variations in vacuum, control the amount of exhaust gas recirculation.
OPERATION:
The port EGR valve is controlled by a flexible diaphragm which is spring loaded to hold the valve closed. Vacuum applied to the top side of the
diaphragm overcomes the spring pressure and opens the valve in the exhaust gas port. This allows the exhaust gas to be pulled into the intake
manifold and enter the engine cylinders.
