GM Full Size Vans 1967-1986 Repair Guide

Diesel Engines

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IDLE SPEED ADJUSTMENT



See Figure 1



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Fig. Fig. 1: 6.2L (379 cu. in.) diesel injection pump showing idle adjustments

A special tachometer suitable for diesel engines must be used. A gasoline engine type tach will not work with the diesel engine.

  1. Set the parking brake and block the drive wheels.
  2.  
  3. Run the engine up to normal operating temperature. The air cleaner must be mounted and all accessories turned off.
  4.  
  5. Install the diesel tachometer as per the manufacturer's instructions.
  6.  
  7. Adjust the low idle speed screw on the fuel injection pump to 650 rpm in Neutral or Park for both manual and automatic transmissions.
  8.  

All idle speeds are to be set within 25 rpm of the specified values.

  1. Adjust the fast idle speed as follows:
    1. Remove the connector from the fast idle solenoid. Use an insulated jumper wire from the battery positive terminal to the solenoid terminal to energize the solenoid.
    2.  
    3. Open the throttle momentarily to ensure that the fast idle solenoid plunger is energized and fully extended.
    4.  
    5. Adjust the extended plunger by turning the hex-head screw to an engine speed of 800 rpm in Neutral.
    6.  
    7. Remove the jumper wire and reinstall the connector to the fast idle solenoid.
    8.  

  2.  
  3. Disconnect and remove the tachometer.
  4.  

 
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