Chevrolet Full Size Cars 1979-1989

Diesel Fuel Injection

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Fig. Fig. 1 CAV-Lucas Injection pump slow idle screw



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Fig. Fig. 2 Roosa-Master injection pump slow idle screw

GM diesel engines are equipped with Roosa-Master, CAV-Lucas, or Stanadyne injection pumps. The Roosa-Master and Stanadyne pumps are nearly identical.

IDLE SPEED ADJUSTMENT



A special tachometer with an RPM counter suitable for 350 V8 diesels is necessary for this adjustment; a standard tach suitable for gasoline engines will not work.

  1. Place the transmission in Park, block the rear wheels and firmly set the parking brake.
  2.  
  3. If necessary, adjust the throttle linkage as described in of this guide.
  4.  
  5. Start the engine and allow it to warm up for 10-15 minutes.
  6.  
  7. Shut off the engine and remove the air cleaner assembly.
  8.  
  9. Clean off any grime from the timing probe holder on the front cover; also clean off the crankshaft balancer rim.
  10.  
  11. Install the magnetic probed end of the tachometer fully into the timing probe holder. Complete the remaining tachometer connections according to the tach manufacturer's instructions.
  12.  
  13. Make sure all electrical accessories are OFF, then disengage the 2 lead connector from the generator.
  14.  

At no time should either the steering wheel or brake pedal be touched.

  1. Start the engine and place the transmission in Drive (after first making sure the parking brake is firmly applied).
  2.  
  3. Check the slow idle speed reading against the one printed on the underhood emissions sticker. Reset if necessary.
  4.  
  5. Unplug the connector from the fast idle cold advance (engine temperature) switch, and install a jumper wire between the connector terminals.
  6.  

DO NOT allow the jumper to ground.

  1. Check the fast idle speed and reset if necessary according to the specification printed on the underhood emissions sticker.
  2.  
  3. Remove the jumper wire and reconnect the temperature switch.
  4.  
  5. Recheck the slow idle speed and reset if necessary.
  6.  
  7. Shut off the engine.
  8.  
  9. Return all disconnected wiring connectors to their original locations.
  10.  
  11. Disconnect and remove the tachometer.
  12.  
  13. If equipped with cruise control, adjust the servo throttle rod to minimum slack, then put the clip in the first free hole closest to the bellcrank or throttle lever.
  14.  
  15. Install the air cleaner assembly.
  16.  

 
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