Positive Pressure Retard

1. Warm engine to operating temperature.
2. Ensure idle speed and ignition timing are within specification.
3. Disconnect vacuum hose to vacuum control and plug end of hose.

Fig. 80 Testing positive pressure retard.:

4. Attach pressure tester 49H080740, Fig. 80. or equivalent to vacuum control.

Fig. 28 Positive pressure spark retard control chart. Turbocharged:

5. Apply compressed air gradually by turning adjusting screw and use timing light to ensure ignition timing retards, Fig. 28.