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.
- Place the transmission in Park, block the rear wheels and firmly set the parking brake.
- If necessary, adjust the throttle linkage as described in of this guide.
- Start the engine and allow it to warm up for 10-15 minutes.
- Shut off the engine and remove the air cleaner assembly.
- Clean off any grime from the timing probe holder on the front cover; also clean off the crankshaft balancer rim.
- 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.
- Make sure all electrical accessories are OFF, then disengage the 2 lead connector from the generator.
At no time should either the steering wheel or brake pedal be touched.
- Start the engine and place the transmission in Drive (after first making sure the parking brake is firmly applied).
- Check the slow idle speed reading against the one printed on the underhood emissions sticker. Reset if necessary.
- Unplug the connector from the fast idle cold advance (engine temperature) switch, and install a jumper wire between the connector terminals.
DO NOT allow the jumper to ground.
- Check the fast idle speed and reset if necessary according to the specification printed on the underhood emissions sticker.
- Remove the jumper wire and reconnect the temperature switch.
- Recheck the slow idle speed and reset if necessary.
- Shut off the engine.
- Return all disconnected wiring connectors to their original locations.
- Disconnect and remove the tachometer.
- 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.
- Install the air cleaner assembly.