Federal Vehicles
The Federal EGR system is operated normally by carburetor ported vacuum. It functions at any engine temperature when the throttle is above idle. However, the system has an overheat mode that operates when coolant is above 113° F (45° C), gearbox is in neutral and choke knob is out. Under these conditions, the solenoid valve is energized and full manifold vacuum is applied to the EGR valve. This full EGR operation prevents overheating.