Cummins/Onan — Cleaning the Carburetor and Combustion Chamber with Onan 4C
Maintenance
From a Cummins/Onan owner's manual — check it applies to your exact model before use.
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Before you start
- Do not allow any spark, flame, pilot light, lit cigarette, or other ignition source near the generator set when performing this procedure.
Procedure
- Start the genset and let it warm up to normal operating temperature.
- Stop the genset.
- Confirm all loads are off and place genset output breakers to Off position.
- Remove the air cleaner housing and air filter.
- Restart the set and spray the 4C into the carburetor, washing the choke plate and inside walls.
- When about an ounce remains, flood the engine until it stops.
- Do not start the engine for 15 minutes while the 4C softens the carbon.
- Place output breakers to On, restart with no load, increase gradually to full load for a few minutes.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.