Vacuum Timing Controls

Fig. 35 Testing Spark Control System:

1. Start the engine and warm-up to normal operating temperature.
2. Connect a strobe timing light and check the ignition timing at idle.

Ignition Timing: Approx. 13° BTDC at Max. 950 rpm

3. Disconnect the distributor sub-diaphragm vacuum hoses and plug the hoses. Fig. 35
4. Check the ignition timing at idle.

Ignition Timing: 5° BTDC at Max. 950 rpm

5. If not as specified, test each component in the system.
6. Reconnect vacuum hoses and disconnect timing light.

Fig. 36 Testing Vacuum Advance:

1. Remove the cap and rotor from the distributor.
2. Remove both vacuum hoses from the sub-diaphragm and plug one of the ports. Fig. 36
3. Apply vacuum to the other port with a handheld vacuum pump.
4. Check that the pick-up plate inside the distributor moves in accordance with the applied vacuum.
5. If a problem is found, replace vacuum advance diaphragm or repair distributor.
6. Reinstall the distributor cap and rotor.

7. Reinstall the distributor cap and rotor. Reconnect vacuum hoses. For further information on the spark control system refer to EMISSION CONTROLS.