GM Full-Size Trucks 1970-1979 Repair Guide

Diesel Fuel Injection

Print

IDLE SPEED ADJUSTMENT



350 V8 Diesel

A special tachometer with an RPM counter suitable for the 8-350 V8 diesel 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 Chassis Electrical .
  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.
  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 probe end of the tachometer fully into the timing probe holder. Complete the remaining tachometer connections according to the tach manufacturer's instructions.
  12.  
  13. Disconnect the two-lead connector from the generator.
  14.  
  15. Make sure all electrical accessories are OFF.
  16.  

At no time should either the steering wheel or the 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 it to the temperature switch.
  4.  
  5. Recheck the slow idle speed and reset if necessary.
  6.  
  7. Shut off the engine.
  8.  
  9. Reconnect the leads at the generator and A/C compressor.
  10.  
  11. Disconnect and remove the tachometer.
  12.  
  13. If the car is equipped with cruise control, adjust the servo throttle rod to minimum slack, then put the clip in the first free hole closest to the bell rank or throttle lever.
  14.  
  15. Install the air cleaner.
  16.  

 
label.common.footer.alt.autozoneLogo