Cummins/Onan — Automatic Choke (Gasoline Sets)
Repair & overhaul
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- Fuel is highly flammable and may cause severe personal injury and property damage. Do not allow cigarettes, flame, pilot lights, arcing switches or equipment in area.
Procedure
- Remove the two wire leads from bi-metal cover assembly.
- Remove insulating boot.
- Remove three screws that secure bi-metal cover assembly to carburetor and remove assembly.
- Install new bi-metal cover assembly, ensuring slot in bi-metal arm assembly straddles and holds outer end of coil spring.
- Install, but do not tighten, the three screws.
- Turn body of bi-metal cover both directions to verify choke plate opens and closes.
- Turn body of bi-metal cover to select appropriate model (JB or JC) and tighten three screws.
- Install insulating boot over bi-metal cover assembly.
- Connect the two wire leads.
- Check operation of vacuum pulloff diaphragm assembly and adjust as required.
Tools required
- screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 12 volts DC at heating element terminals during engine starting
- heater resistance about 2.5 to 3 ohms at room temperature
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.