12 13... Normal oscillogram (M, S, W engines only)

Start of ignition voltage peak. See Fig 1.
Level of ignition voltage. See Fig 1.
Level of combustion voltage. See Fig 1.
Period of combustion. See Fig 1.
Combustion curve characteristics. See Fig 1.
Start of decay process. See Fig 1.
Termination oscillations. See Fig 1.

Fig 1: Identifying Oscilloscope Pattern
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Secondary voltage patterns, beside one another:

Evaluation of ignition voltage peaks at idle speed (this example shows an engine with 4 cylinders). See Fig 2.

Fig 2: Secondary Voltage Patterns (Beside One Another)

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NOTE: The display of ignition voltage spikes is approx. 20-25% lower than the real value.

The uniformity of all cylinders to each other is more important than the height of ignition voltage peaks. Differences of 30 00... 4000 V are permitted.

In event of greater differences, diagnose ignition system.

Evaluation of ignition voltage peaks at increased speed of approx. 2000 RPM (this example shows an engine with 4 cylinders).

Fig 3: Ignition Voltage Oscilloscope Pattern

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Secondary voltage diagrams, superimposed:

Evaluation of combustion characteristics curve and decay characteristics at idle speed (this example shows a 4-cylinder engine). See Fig 4.

Fig 4: Secondary Voltage Diagrams (Superimposed)

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Secondary voltage diagrams, consecutive:

NOTE: Only the major differences in the ignition voltage patterns are revealed by this method of comparison.

The identified fault must be allocated to the relevant cylinder using the secondary voltage representation forms next to/on top of each other. See Fig 5.

Fig 5: Secondary Voltage Diagrams (Consecutive)

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