Further Fault Patterns With Evaluation.

Evaluation of Sparking Period and Ignition Voltage Peaks at Idling Speed





1 Normal sparking period.
2 Normal ignition voltage peak. Ignition system is okay





Long sparking period (1) with low ignition voltage peak (2). Indicates low compression.
Fluctuating sparking period. Indicates contamination on spark plug (shunt).





Short sparking period (1) with high ignition voltage peak (2).
Constant but short sparking period: Indicates defective ignition lead.

NOTE: The sparking voltage line could sometimes be missing completely and the ignition voltage peak could rise very high.

Ignition Voltage Too High:
- Electrode gap - Large
- Compression - High
- Fuel air mixture - Lean
- Electrode temperature - Low
- Electrode condition - Burnt
- Ignition lead - Interrupted

Ignition Voltage Too Low:
- Electrode gap - Small
- Compression - Low
- Fuel air mixture - Correct
- Electrode temperature - High
- Electrode condition - New