Check the boring stuff first
Fuel level: most motorhome generators draw from the main fuel tank through a pickup tube that sits above the bottom — by design, the genset stops drawing when the tank drops to about a quarter. It's there so the generator can't run your driving fuel dry, and it catches people constantly. Below a quarter tank, a healthy generator simply won't run.
Then: battery voltage (the genset cranks off the house batteries — weak batteries mean slow crank and no start), the oil level (most units have a low-oil shutdown that kills it immediately after start), and any tripped breakers on the generator's own face.
Reading the blink code
Onan units tell you what's wrong: when the unit faults, the status light blinks a code — press the stop button briefly and count the pattern, then match the code in your manual. Fuel starvation, low oil pressure, over-temperature, and under-voltage each have their own number.
That one trick separates "it needs fuel" from "it needs a technician" in thirty seconds, so do it before tearing anything apart.
Stale fuel and the varnished carburetor
Gasoline starts degrading in about a month and is genuinely stale by three — it loses volatility and leaves varnish that clogs the tiny jets in a carburetor. A generator that sat all winter, then starts hard, hunts, and surges (rev up, rev down, over and over) is textbook varnish.
Sometimes you get lucky: fresh fuel, a fuel stabilizer, and a long run under load will clean a lightly-gummed carb. Past that, the fix is pulling and cleaning the carburetor or — often cheaper in labor than a deep cleaning — replacing it outright. Priming the system first (hold the prime button 30–60 seconds) refills the fuel line and float bowl after any long sit.
Surging under load vs. surging at idle
No-load surging on a carbureted genset is usually fuel delivery (varnish, partially clogged jet, weak fuel pump, dirty fuel filter). Surging only when the AC kicks on points instead at overload — a 3,000-watt unit starting a 13,500-BTU AC compressor is right at its limit, and high altitude makes it worse: naturally-aspirated engines lose roughly 3% of their power per 1,000 feet of elevation.
If you camp high, that's not a defect — it's physics. Shed load (turn off the electric water heater element and microwave before the AC starts), or have the carb's altitude jetting adjusted if the unit supports it.
The two-hour rule that prevents all of this
Generators die from sitting, not from running. Once a month, run the genset for two hours under at least half load — an AC or a space heater, not idle. That burns off moisture, keeps fuel moving through the carb, and keeps seals from drying out. It's the single highest-value habit an RV owner can keep.
Add fuel stabilizer before storage, and your odds of a first-pull spring start go way up.
Stuck on this one? Put Major in your pocket.
Tell RV Journey Genie your make, model, and symptom and get a step-by-step fix — by text, voice, or photo — before you ever call the shop.
Frequently asked questions
Why won't my RV generator start with a quarter tank of fuel?
That's by design. Motorhome generators draw fuel through a pickup tube that sits above the bottom of the main tank, so the generator stops drawing at roughly a quarter tank. It prevents the genset from running your driving fuel dry. Fill the tank and it will start drawing again.
Why does my RV generator surge up and down?
Rhythmic surging or "hunting" at no load is almost always fuel delivery — stale gas varnish clogging the carburetor jets, a dirty fuel filter, or a weak pump. Surging only under heavy load (like AC startup) points to overload or high-altitude power loss instead. Fresh fuel and a carb cleaning fix most cases.
How often should I run my RV generator?
Exercise it monthly: two hours under at least 50% load. Running under load burns off moisture, keeps carburetor fuel fresh, and prevents the varnish buildup that causes hard starts and surging. A generator that sits unused for months is far more likely to fail than one that's run regularly.