Correct Secondary Patterns

Good Secondary Oscilloscope Pattern:

A correct secondary pattern (superimposed) should reveal proper:

^ Ignition voltage line height (Firing Line)
^ Burn time
^ Burn voltage
^ Burn voltage line
^ Decay process
^ Primary current limiting
^ Coil open circuit time
^ Coil closed circuit time (Dwell)

Good Secondary (Parade) Pattern:

With the engine running at idle RPM the parade pattern should indicate ignition voltage line heights between (6-16 kV). The maximum difference between cylinders should not vary by more than (3 kV).

Good Secondary Pattern (Parade):

While repeatedly accelerating the engine to approx. 3000 RPM the ignition voltage lines show a uniform increase at all cylinders. The ignition voltage increase should not exceed 6 kV.

Good Secondary (Raster) Pattern:

A raster comparison should indicate identical patterns for each cylinder with the exception of possible intermittent primary current limitation.

Good Decay Process (Bosch Ignition Coil/Green Sticker):

The decay process should indicate 5-6 oscillations (Bosch coils with green label).

Good Secondary Pattern (May Christi Ignition Coil):

The decay process should indicate 8-9 oscillations (May Christi coil with green label or Bosch coil with yellow label)

Good Primary Pattern (Current Limiting):

Primary current limiting can occur intermittently at one or all cylinders at engine speeds below 2000 RPM with or without a load.


If the elements of the scope patterns above are not present a problem is indicated.

NOTE: Oscilloscope patterns vary from one manufacturer to another.
Always check the manufactures operating manual for exact pattern display and tester connections.

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