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12 13... Further fault patterns with evaluation

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

  1. Normal combustion period.
  2. Normal ignition voltage peak.
Fig 1: Fault Pattern Of Normal System
G00397835Courtesy of BMW OF NORTH AMERICA, INC.

Ignition system is OK.

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

Fig 2: View Of Long Sparking Period
G00397836Courtesy of BMW OF NORTH AMERICA, INC.

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
G00397837Courtesy of BMW OF NORTH AMERICA, INC.

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
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