Additional Fault Patterns

ADDITIONAL FAULT PATTERNS:

Evaluation of combustion period of ignition voltage spikes at idle speed:




1. Normal combustion period.
2. Normal ignition voltage spike. Ignition system OK.




- Long combustion period (1) with low ignition voltage spike (2): Suggestive of low compression.
- Fluctuating combustion period: Suggestive of impurities in spark plug (shunt).




- Short combustion period (1) with high ignition voltage spike.
- Constant but brief combustion period: Suggestive of defective ignition cable.

NOTE: The combustion voltage curve may be entirely absent and the ignition voltage spike may be very high.

Excessive Ignition Voltage:

Electrode gap: large
Compression: high
Fuel mixture formation: lean
Electrode temperature: low
Electrode gap: burned out
Ignition cable: interrupted

Excessively Low Ignition Voltage:

Electrode gap: small
Compression: low
Fuel mixture formation: correct
Electrode temperature: high
Electrode condition: new