Altitude Compensator: Testing and Inspection

Fig. 17 High altitude compensation system.:

Fig. 18 Connecting vacuum pump.:

This procedure is for sea level areas only.
1. Warm engine to operating temperature and run at idle.
2. Ensure ignition timing is approximately 7° BTDC with vacuum connected.
3. Connect vacuum pump to atmospheric pressure sensor Fig. 18.
4. Apply a vacuum of 4.72 inches Hg and ensure ignition timing is approximately 13° BTDC.
5. If system is not operating satisfactorily, test atmospheric pressure sensor and engine control unit as described in ``Gasoline Fuel Injection.''