EGR System - Diesel: Operation
Below a predetermined temperature, when engine coolant is not warm, no exhaust gas recirculation will occur since the thermal vacuum switch is closed. Once coolant warms up, the thermal vacuum switch opens and exhaust gas recirculation is then controlled by the other components of the system.
EGR volume is controlled by, depending on model, EVRV or VRV output vacuum in accordance with injection pump lever on pump lever angle.