Cummins/Onan — Checking Advance Mechanism

Testing & diagnosis · Spark advance mechanism

From a Cummins/Onan service manual — check it applies to your exact model before use.

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Procedure

1. The timing marks will be visible through the flywheel.
2. Connect timing light to spark plug.
3. Start engine and run at 1500 rpm or over.
4. View timing marks using timing light. Flywheel mark should align with mark on gear cover.
5. While watching timing marks with timing light, slow engine to below 800 rpm. If timing marks are not aligned but realign when engine is brought back to speed, mechanism is operating properly.
6. If ignition advance mechanism does not react as described in step 5, remove, clean and/or replace as necessary.
7. Replace cover.

Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.

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