Cummins/Onan 6.5NH - 3CR / 6000 A — Spark Advance Mechanism Check (Contractor Model)
Testing & diagnosis
For the Cummins/Onan 6.5NH - 3CR / 6000 A, from the Cummins/Onan service manual.
Applies to: Cummins/Onan NH engine
Procedure
- Timing marks are visible through the flywheel.
- Connect a timing light to a spark plug.
- Start the engine and run at 3600 rpm.
- View the timing marks with the light; the TC flywheel mark should align with the TC mark on the gear cover.
- While watching the marks, slow the engine to below 800 rpm; the TC mark should disappear and reappear when the engine is brought back to speed.
- If the mechanism does not react, remove, clean and/or replace as necessary; replace the cover.
Tools required
- Timing light Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Check at 3600 rpm
- Check below 800 rpm
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.