Cummins/Onan — Timing Check - Engine Running
Testing & diagnosis · Ignition timing
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan NHP / NHPV engine
Procedure
- Connect a timing light according to its manufacturer's instructions.
- Either spark plug can be used as they fire simultaneously.
- Start engine and check timing at idle speed.
- Pointer on flywheel should line up with 25 degree mark on cover.
- If marks do not line up, readjust point gap (open to advance, close to retard).
- Recheck timing and breaker point gap after adjustment.
Tools required
- Timing light Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 25 degrees BTC
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.