GM Cadillac 1967-1989 Repair Guide

Exhaust Gas Recirculation (EGR)

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See Figures 1, 2, 3, 4, 5 and 6

To lower the formation of nitrogen oxides (NOx) 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.



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Fig. Fig. 1: EGR system diagnosis - diesel engine



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Fig. Fig. 2: Diesel vacuum regulator valve - mounted to injection pump



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Fig. Fig. 3: Diesel EGR valve location



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Fig. Fig. 4: Diesel EGR system - except California



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Fig. Fig. 5: California EGR system - V8 diesel



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Fig. Fig. 6: Diesel EGR vacuum reducer - except California

FUNCTIONAL TESTS OF COMPONENTS



Vacuum Regulator Valve (VRV)

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 it is 6 inches; at wide open throttle there is no vacuum.

Exhaust Gas Recirculation (EGR) Valve

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

Response Vacuum Reducer (RVR)

Connect a vacuum gage 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:

  1. 0.75 in.Hg - Except High Altitude
  2.  
  3. 2.5 in.Hg - High Altitude
  4.  

Torque Converter Clutch Operated Solenoid

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

SOLENOID ENERGIZED



  1. Ports 1 and 3 are connected.
  2.  

SOLENOID DE-ENERGIZED
  1. Ports 2 and 3 are connected.
  2.  

 
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