Detonation Sensor Test
1. Connect a suitable timing light to the engine.
2. Start engine and increase speed to 1200 RPM.
3. Connect a suitable vacuum pump to the vacuum transducer. Set pump to 16 inches vacuum.
4. Tap on the manifold near the sensor. Using the timing light, check for a decrease in spark advance. The amount of decrease in timing is proportional to the strength and frequency of the tapping. The greatest decrease in timing will be approximately 11 degrees.