Chevrolet Full Size Cars 1979-1989

Exhaust Gas Recirculation (EGR)


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Fig. Fig. 1 Diesel EGR system except California vehicles

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Fig. Fig. 2 California EGR system V8 diesel engine

To lower the formation of nitrogen oxides (NO x ) in the exhaust, it is necessary to reduce combustion temperatures. This is accomplished with diesel engines in the same method as with gasoline engines, by introducing small amount of exhaust gases into the cylinders using an EGR valve.


Vacuum Regulator Valve (VRV)

The Vacuum Regulator Valve is attached to the side of the injection pump and regulates vacuum in proportion to throttle angel. Vacuum from the vacuum pump is supplied to port A and vacuum at port B is reduced as the throttle is opened. At closed throttle, the vacuum is 15 in. Hg; at half throttle, 6 in. Hg; at wide open throttle there is no vacuum.

Exhaust Gas Recirculation (EGR) Valve

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Fig. Fig. 3 The diesel EGR valve is located on top of the intake manifold

Apply vacuum to vacuum port. The valve should be fully open at 10.6 in. Hg and closed below 6 in. Hg.

Response Vacuum Reducer (RVR)

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Fig. Fig. 4 Diesel vacuum reducer except California

The Response Vacuum Reducer (sometimes known as the vacuum reducer valve) may be tested using a hand vacuum pump. Connect a vacuum gauge to the port marked To EGR valve or T.C.C solenoid. Connect a hand operated vacuum pump to the RVR port. Draw a 15 in. Hg (50.66 kPa) vacuum on the pump and the reading on the vacuum gauge should be lower than the vacuum pump reading as follows: 1980-83.

0.75 in. Hg (2.53 kPa) Except High Altitude
2.50 in. Hg (8.44 kPa) High Altitude 1984-85
2.00 in. Hg (6.75 kPa)

Torque Converter Clutch Operated Solenoid

When the torque converter clutch is engaged, an electrical signal energizes the solenoid allowing ports 1 and 2 to be interconnected. When the solenoid is not energized, port 1 is closed and ports 2 and 3 are interconnected.

Solenoid Energized

Ports 1 and 3 are connected.

Solenoid De-energized

Ports 2 and 3 are connected.