Cummins/Onan — Ignition Timing
Adjustments · Distributor
From a Cummins/Onan owner's manual — check it applies to your exact model before use.
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Before you start
- Continuous ping indicates excessive advance; no ping indicates timing should be advanced.
Procedure
- Set distributor contact points to 0.020 in. gap at full separation.
- Remove flywheel inspection hole cover and turn engine until No. 1 piston comes up on compression stroke.
- Crank slowly until flywheel mark centers in the inspection hole.
- Distributor rotor should point to the No. 1 spark plug wire tower and points should just separate.
- If rotor points to No. 4 tower, remove distributor and turn drive shaft one half turn.
- Start plant, reach operating temperature, and test spark advance by applying full electrical load.
- Loosen distributor clamp and turn body clockwise to advance or counterclockwise to retard.
- Retighten clamp screw; keep spark advanced as far as possible without pinging.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Contact points 0.020 in.
Source: Cummins/Onan owner's 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.