Why Generator Maintenance Gets Neglected
The generator gets ignored until it's needed — and then it doesn't start. Generators that sit unused for months with old fuel are one of the most common RV mechanical failures. Unlike the RV's engine (which most owners remember to service), the generator gets put away at the end of the camping season and forgotten until the next trip.
The good news: generator maintenance is straightforward and cheap. The intervals are longer than a car engine, the parts are inexpensive, and most work is DIY-accessible.
Onan and Built-In Generator Maintenance (Gas/Diesel)
Most Class A and many Class C motorhomes have Cummins Onan built-in generators. Diesel pusher coaches have diesel generators; gas chassis coaches have gasoline generators.
Oil changes: Change oil every 100 hours of operation or annually, whichever comes first. The hour meter on the control panel tracks this. Onan specifies oil weight and type in the owner's manual — typically 15W-40 or 5W-30 depending on the unit. This is a 30-minute job with an oil drain pan and the correct filter.
Air filter: Inspect every 50 hours, replace as needed (typically every 200 hours or when dirty). A clogged air filter causes hard starting, low power output, and high fuel consumption.
Spark plugs (gas units): Replace every 150 hours or annually. Worn plugs cause hard starting and rough running. The plug type is specified in the owner's manual — don't substitute.
Fuel filter: Replace annually or per the manual interval. Old fuel and sediment in the filter are a common cause of starting problems.
Coolant (liquid-cooled units): Check coolant level seasonally. Flush and replace per the service manual (typically every 2 years or 500 hours).
Portable Generator Maintenance (Champion, Honda, Generac)
Portable generators (Honda EU series, Champion, Generac) carried by fifth wheels and travel trailers have similar maintenance requirements but shorter intervals due to air-cooled designs:
Oil changes: First change at 20 hours (break-in), then every 50–100 hours depending on manufacturer. Honda recommends every 50 hours; Champion every 100 hours. Check the level before every use — small engines consume oil under load.
Spark plug: Inspect every 100 hours, replace every 300 hours or annually.
Air filter: Clean foam filter every 50 hours, replace every 200 hours.
Carburetor: The most common failure point. Old fuel leaves varnish deposits that clog jets. Run the generator dry at the end of the season (run until fuel starvation) or use fuel stabilizer (Sta-Bil) in the tank. If you skipped this and the generator won't start, carburetor cleaner spray or a full carburetor cleaning kit ($15) often fixes the problem.
The Fuel Problem (Most Common Failure)
Ethanol-blended gasoline (E10) is the enemy of small engines that sit unused. Ethanol absorbs moisture from the air, the fuel separates, and the water-ethanol layer sinks to the carb bowl where it corrodes jets and causes varnish deposits. This happens in 30–60 days in humid conditions.
Solution 1 — Fuel stabilizer: Add Sta-Bil, Star Tron, or similar stabilizer to the fuel tank before storage. Run the generator for 5–10 minutes to get the treated fuel into the carburetor. Good for 12–24 months.
Solution 2 — Run dry: Close the fuel valve and let the generator run until it dies from fuel starvation. Empties the carburetor bowl and prevents varnish formation.
Solution 3 — Non-ethanol fuel: Use pure gasoline (no ethanol) where available. Non-ethanol fuel doesn't phase-separate and stores much longer. The premium price is worth it for generator fuel.
Monthly Exercise (Critical for Storage)
Run the generator under load for at least 30 minutes every month during storage periods. "Under load" means actually running the AC unit or other high-draw appliances — not just idling. This keeps the fuel system active, charges the battery (built-in units), exercises seals and gaskets, and identifies problems before they compound.
The biggest mistake: letting a generator sit for 6 months without running it, then expecting it to start on the first cold morning of the camping season.
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