EGR Control Solenoid: Description and Operation

This switch is used on some V8-350 diesel engines. When vacuum at this switch is below 8 inches Hg, the switch's electrical contacts are normally closed. Regulated vacuum from the vacuum regulator valve is directed to the EGR-VS. When vacuum is above 8 inches Hg, the switch's electrical contacts close and complete the circuit to ground. The EGR vacuum solenoid valve is energized allowing unregulated vacuum from the vacuum pump to be directed through the EGR vacuum solenoid valve to the EGR valve.