Oscilloscope Patterns and Waveforms

SECONDARY IGNITION SYSTEM DISPLAY DIAGNOSIS

PROCEDURE
1. Connect an engine analyzer to view parade display of secondary ignition system.

2. Start the engine and slowly increase engine speed from idle to 2000 rpm.

3. Compare the engine analyzer display to the following display illustrations in the Evaluation of Secondary Display.

EVALUATION OF SECONDARY DISPLAY






Result 1
The average value of spark plug firing voltage is 15 kilovolts or less with evenness of spark plug firing voltage 5 kilovolts or less.

If the result is as indicated, the ignition system is OK.






Result 2
The average value of spark plug firing voltage is greater than 15 kilovolts with evenness of spark plug firing voltage 5 kilovolts or less.

If the result is as indicated, check the following:
- Spark plug gap.






Result 3
Evenness of spark plug firing voltage is greater than 5 kilovolts.

If the result is as indicated, check the following:
- Spark plug gap.






Result 4
Consistently high spark plug firing voltage in one or more cylinders.

If the result is as indicated, check the following:
- High-tension lead connections.
- Spark plug gap.
- Resistance of high-tension leads






Result 5
Consistently low spark plug firing voltage or stopping spark line in one or more cylinders.

If the result is as indicated, check the following:
- Fouled spark plugs.
- Spark plug gap.
- Grounded high-tension leads.






Result 6
Spark plug firing voltage negative going.

If the result is as indicated, check the following:
- Ignition coil for reversed primary circuit.
- Wiring harness
- Ignition coil