Dear Dave,
I can’t get my RV’s generator to stay on. We replaced the battery in back. Could it possibly be a fuse that’s causing the problem? —Audrey, 2013 Coachmen Freelander
Dear Audrey,
From what I can tell on various dealer walkarounds, your generator could be either an Onan (Cummins) or Generac; however, most opted for the 4000-watt Onan gas version. Typically the generator uses the house battery/batteries to turn over and start. So, I’m not sure what “battery in back” you are referring to unless it is the house battery. This is only designed to turn the starter and not keep the unit running. Since you indicated you can’t get it to “stay on,” it must mean it is turning over and starting, just not staying on? If that is the case, it would not be the battery or a fuse, as those are only providing power and it would not even attempt to turn over.
There are three basic components when it comes to troubleshooting a gas engine issue: power, spark, and fuel. Power and spark sometimes are related issues. However, if the engine is turning over and attempts to start, then we can rule out power, as we discussed, and look at spark and fuel.
Fuel
Gasoline is drawn from the main fuel tank of your Ford chassis with the draw at approximately 1/4 tank level. This is to prevent the generator from running the tank out of gas and leaving you stranded. I have found some of these to be way higher than 1/4 level, almost to the 1/2 level. So the first thing I would suggest is to start with at least 3/4 tank of fuel, just to make sure.
The fuel is drawn out of the tank by a fuel pump and passes through a fuel filter before going to the carburetor. I would suggest changing the fuel filter and see if that helps. If not, you can remove the fuel line and verify there is fuel being pumped to the generator. If not, you have found the issue.
Since you rig is over 10 years old, the generator may have a high altitude switch or even a winter/summer lever. Both of these adjust the fuel-to air-mix ratio and could be making the generator run too lean or too rich.
Varnish
A common issue with gasoline generators is today’s fuel breaks down quickly and creates varnish in the carburetor. It is recommended that you run the generator at 50% load for 30 minutes every month to clean it out, and use a fuel stabilizer during storage. This generally requires a rebuild by a professional. However, I have been able to remove the fuel line and insert it into a gallon of fuel with a heavy dose of Seafoam. Onan has their own fuel stabilizer that they recommend. You might try adding some to the tank and see if it will cycle through and work.
Spark
Next, there needs to be a spark from the sparkplug, which can be tested by removing the plug and grounding it to the base. With the plug wire attached, turn over the unit and verify there is spark. A dirty plug or improper gap can also be an issue. However, if it does start initially and run for a short time, there typically would not be a spark.
One more thing
Actually, two more things. If the oil level is low, it will sense that and shut down once it gets to temperature. Also, it will do the same thing if the air filter is plugged. I would suggest changing the oil and filter as well as the air filter, just to be sure. And I suggest using Onan-recommended parts, as not all filters are high-quality and can provide a false reading.
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Dear Dave,
Our Tiffin 32BA FRED carries an onboard diesel 6000w Onan generator in a compartment. It can activate with a switch on the generator itself but we’ve always used the remote switch on the dash. Last week, neither switch started the generator until I started the RV engine. There was just a clicking sound. Is/are there fuse(s) I need to check? Any other suggestions? —Tim, 2007 Tiffin Allegro Open Road front-engine diesel [FRED]
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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One more possibility – if it starts and then dies when you release the start switch, it’s a problem with the generator itself. Onans have a safety feature that stops the engine if there is no AC output – a safety that is locked out until you release the start switch. It could be a problem with the generator itself, worn brushes or dirty slip rings, or a bad voltage regulator.
Install a fuel cutoff valve in the fuel line. Run the carb dry after using the genset. Helps keep today’s fuels from gumming up the carb.
The two preceding comments are good additional points. But starting with the most likely, easiest and least expensive, I go with Dave’s suggestion of the fuel filter.
A partially clogged filter will pass fuel, but slower. Between runs the filter passes enough fuel to start the engine, but the engine’s demands quickly exceed the filter’s current flow capacity causing the engine to stall. During shutdown, fuel is replenished and the cycle starts over.
I’ll throw in another scenario since we don’t know how long it is running before shut off. The generator typically does not have a charging circuit. If the battery is only hooked up to the generator and nothing else it may be running down which will kill the engine (the generator needs battery power to keep running). I found this out the hard way after dealer set in a generator battery that had no means of recharging. Generator would run a couple of days (it was a new and healthy battery) and then mysteriously shut down.
If the generator is running long enough to warm up, it could also be a weak fuel pump. I had a new Onan gas generator that would start up fine and run for 5 to perhaps 20 minutes then chug and stop. The dealer did all the usual testing and could not find any issues.
I called Onan and they immediately diagnosed it as a bad fuel pump. Took it directly to Onan and they changed it out on warranty. Never had a problem again for the eight years we owned it.
That said, your starter switch should have a light that blinks when it dies. That blinking is a diagnosis code that can help narrow the search for the issue. Dig out your owners manual or contact Onan directly.
We lost all power inside of the motorhome..we checked all fuses..no problem..the generator runs great no problem but still no power inside the motorhome? Suggestion welcome
Don’t forget to plug generator back in. I’ve forgotten that simple task before.
Mine has a breaker switch on the generator
If it has a low oil sensor and the oil is full but it still shuts off change the oil. Oil that is contaminated by fuel will set off the sensor circuit and keep the engine from running.
Good point Roger B. My Generac kept shutting down after running for a few minutes. Changed the oil and filter and it has been running fine ever since.
The problem was probably a fellow camper flipping the switch on that noisy generator. Put out a solar panel, or two, and let your neighbors camp in peace!
Thank you, Dave!
I had a similar problem on my 2023 Thor Vegas. Occasionally I could not get the generator to start. Onan help line said to check available voltage to the generator. I have a portable jumper pack that I hooked up to the generator and it started no problem. Disconnected the pack and it stalls. Then I remembered seeing a spark in the battery compartment near a 100 amp circuit breaker. Thinking it might be the issue I bought a new one and then dug out the old one from the dark and hard to reach location under the stairs. To my surprise the cable on the bottom of the circuit breaker was very loose. During assembly the nut was cross threaded so it appears tight but was making and breaking contact.
Dave how about when you are driving & running generator to power the A/C units in hot weather, & Gen shuts off. Happened several times to us, especially this past yr when temps in TX were very hi. Started Gen right back up & ran for hrs. So no battery, fuel, or spark issues. Does Gen have over heat shut off? But it starts right back up. 2016 Bounder with 5.5 Onan Gen.