12 13... Further fault patterns with evaluation

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Evaluation of sparking period and ignition voltage peaks at idling speed.

Normal combustion period.
Normal ignition voltage peak.

Fig 1: Fault Pattern Of Normal System

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Ignition system is OK.

Long sparking period (1) with low ignition voltage peak (2). Indicates low compression.

Fig 2: View Of Long Sparking Period

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Fluctuating sparking period: Indicates contamination on spark plug (shunt).

Short sparking period (1) with high ignition voltage peak.

Fig 3: View Of Short Sparking Period

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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