220 Models
Exhaust gas recirculation only occurs when engine is operated above idle speed but below 3600 RPM with oil temperature above 77°F. Various controls operate as follows: At idle speed, vacuum is insufficient to operate EGR valve. At 3600 RPM, RPM switch opens which causes vacuum control valve to close off vacuum to EGR valve. With oil temperature below 77°F, oil temperature switch is closed which causes vacuum control valve to cut off vacuum to EGR valve by means of relay box.