Repair Pontiac Mid-size 1974-1983 Repair Guide

Exhaust Gas Recirculation (EGR) System

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OPERATION





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Fig. Fig. 1



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Fig. Fig. 2 Diesel EGR system schematic-except California engines



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Fig. Fig. 3 Diesel EGR system schematic-California engines

To lower the formation of nitrogen oxides (NO;zx) in the exhaust, it is necessary to reduce combustion temperatures. This is done in the diesel, as in the gasoline engine, by introducing exhaust gases into the cylinders through the EGR valve.

FUNCTIONAL TESTS OF COMPONENTS



Vacuum Regulator Valve (VRV)


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Fig. Fig. 4 The diesel vacuum regulator valve is mounted to the injection pump

The Vacuum Regulator Valve is attached to the side of the injection pump and regulates vacuum in proportion to throttle angle. 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 inches; at half throttle-6 inches; at wide open throttle there is zero vacuum.

Exhaust Gas Recirculation (EGR) Valve


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Fig. Fig. 5 Diesel EGR valve location

Apply vacuum to vacuum port. The valve should be fully open at 10.5 inch and closed below 6 inch.

Resp


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Fig. Fig. 6 Diesel EGR system response vacuum reducer-except California engines

Ronse Vacuum Reducer (RVR)

Connect a vacuum gauge to the port marked "To EGR valve or T.C.C. solenoid." Connect a hand operated vacuum pump to the VRV port. Draw a 50.66 kPa (15 inch) vacuum on the pump and the reading on the vacuum gauge should be lower than the vacuum pump reading as follows:



0.75 inch Except High Altitude
 
2.5 inch High Altitude
 

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.
 

 
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