Cummins/Onan — Ignition Timing, Two-Cylinder Plant Stopped
Adjustments · Ignition system
From a Cummins/Onan service manual covering: 10.0JC, 12.5JC, 15.0JC, 4.0JB, 5.0JB, 6.0JB, 6.1JB, 7.5JB, 7.6JB. Check it applies to your exact model before use.
Applies to: Cummins/Onan 10.0JC, Cummins/Onan 12.5JC, Cummins/Onan 15.0JC, Cummins/Onan 5.0JB, Cummins/Onan 6.0JB, Cummins/Onan JB engine, Cummins/Onan JC engine
Before you start
- Adjust breaker point gap before timing the ignition.
Procedure
- Remove air housing access door and breaker points cover; disconnect ignition lead and install continuity test lamp and battery.
- Rotate flywheel clockwise until TC mark approaches timing indicator, then slowly until light goes out (points open).
- If incorrect, align 50 ATC mark with pointer, loosen breaker plate capscrews and rotate plate until light goes out.
- Tighten plate and recheck timing, then connect ignition lead and install cover.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Breaker point gap .020 in.
- Timing (stopped) 5 ATC, (running) 25 BTC
Full service-parts list: Cummins/Onan 10.0JC →, Cummins/Onan 12.5JC →, Cummins/Onan 15.0JC →, Cummins/Onan 5.0JB →, Cummins/Onan 6.0JB →
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.