Generator problems.

[glennaeichmann]

Hello. I have a 5500 Onan, It wont start. It has gas and a good battery. If I spray starting fluid in it it will run as long as I keep spraying into the carb. So I know it has gas and spark.... I took the carb off and took it apart and it is clean and the orifices are clear. Air cleaner is good, both fuel filters are good I don't see anything wrong. Now.... If I prime it for about a minute it will run for a second. I pulled the fuel hose off the carb and turned it over and I do have gas coming out of the hose... Any Ideas

[chuckster57]

Sounds like the carb to me. Could be the fuel pump, but I’m leaning towards the carb.

[jasin1]

Originally Posted by glennaeichmann

Hello. I have a 5500 Onan, It wont start. It has gas and a good battery. If I spray starting fluid in it it will run as long as I keep spraying into the carb. So I know it has gas and spark.... I took the carb off and took it apart and it is clean and the orifices are clear. Air cleaner is good, both fuel filters are good I don't see anything wrong. Now.... If I prime it for about a minute it will run for a second. I pulled the fuel hose off the carb and turned it over and I do have gas coming out of the hose... Any Ideas

does it have a bowl mounted fuel cutoff solenoid? if so it may be bad or have a wiring issue for the solenoid…i have a riding mower that used to cutoff intermittently and the solenoid wire was chafed and shorting to the engine case.

[gearhead]

I’d be pricing a new carb. Assuming you are running ethanol gas in it, do you run it dry after use? Are you using a fuel stabilizer?

[Sean D]

Air, spark, & fuel is what you need! Once you find out which one your missing you’ll be able to hone into your issue.

[GlasNav]

Sounds like a varnished carburetor, most likely gummed up because the fuel wasn't shut off and allowed to run dry the last time it was used. (Last Season?)

If you're mechanically inclined, get a carb rebuild kit along with a large can of carb cleaner and rebuild it. If it is varnished and gummed up, you will only need a full gasket set.

[notanlines]

Bypass any rebuild ideas. A new carb is the way to go with the 5500. $50 to $60 all over the ‘net.

[JRTJH]

I agree with Jim. Based on your first post: "If I spray starting fluid in it it will run as long as I keep spraying into the carb. So I know it has gas and spark...."

If it stops running when you stop spraying, it does not have "gas" (it has ether from your spray). So, it has "air and spark", but when the ether (sub for gas) is stopped, it loses gas...

You have a plugged carb passage somewhere. If you spend the time rebuilding it and "miss that one tiny passage" you've wasted the time and expense.

Cut to the chase and just buy a replacement carb, install it and be done with it.

[GlasNav]

If there isn't already a shut off valve in the fuel line, it's recommended that you install one near the generator. Should there be any extended period that you won't be using the generator, start the generator, close the fuel shut off valve and let the engine run until it stalls out due to lack of fuel. Shut off your switch and you shouldn't have this problem again. When you need to use the generator afterwards, open the fuel shut off and start, doubt you will have any further issues with the carb.

[skids]

It seems that the float is not free to operate the fuel valve.

[skids]

BTW, with some carbs, sometimes you can free up a stuck float be tapping on the carb with a screwdriver handle.

[firestation12]

Originally Posted by jasin1

does it have a bowl mounted fuel cutoff solenoid? if so it may be bad or have a wiring issue for the solenoid…i have a riding mower that used to cutoff intermittently and the solenoid wire was chafed and shorting to the engine case.

My 6 boys and I all have RVs with the Onan 5500 generators. There are several issues I’ve had to contend with, but I’ll focus on what I’ve found relative to the symptoms you’ve described. As mentioned above, your carb has a fuel cutoff solenoid attached. If you have fuel in the carburetor bowl, then the solenoid is not the issue. Start with that by removing it and making sure the spring and plunger move freely. If no fuel in the bowl, but fuel in the rubber hose attaching to the cutoff solenoid, then start with that by removing the cutoff solenoid and making sure the spring and plunger move freely. The solenoid sticking has presented itself twice in the family’s RV group. Assuming you have fuel in the bowl, then you have a decision to make of either replacing the carb with an OEM Onan ($400), installing a Chinese knockoff, or relying to resurrect (Easter was last week) your existing carb. I’ve had limited luck with carbs from China. Primarily the ease of starting without a lot of priming. The difficulty in starting is related to finicky choke mechanisms the China carbs seem to have. I do keep a spare China carb on hand for when time does not permit trying to fix the OEM carb. In my opinion, the OEM carb is worth trying first to fix because….it will likely work better than the China offerings. The Onan 5500 carb is flawed in that it has one internal passage that is not accessible. Immersing the carb in Sea Foam for 2 days then using high pressure air to purge all visible openings would be your first try. I still have a container from years back of Gunk® carb cleaner that I use. It’s not the spray can type you find now, but if you can find it, it comes in a gallon size can and employs a metal basket that holds the disassembled carb parts that are then immersed in the solution. If you can successfully remove the blockage in that hidden passageway, you will have the best starting and running generator. I suspect there are forum members out there that have managed to get one of the China carbs that work properly. After 3 tries I’m not one of them.

[Don77]

Originally Posted by glennaeichmann

hello. I have a 5500 onan, it wont start. It has gas and a good battery. If i spray starting fluid in it it will run as long as i keep spraying into the carb. So i know it has gas and spark.... I took the carb off and took it apart and it is clean and the orifices are clear. Air cleaner is good, both fuel filters are good i don't see anything wrong. Now.... If i prime it for about a minute it will run for a second. I pulled the fuel hose off the carb and turned it over and i do have gas coming out of the hose... Any ideas

origanal post is sept 2022

[wiredgeorge]

Crud can get into your fuel shutoff solenoid as has been pointed out. Cleaning the solenoid isn't a bad idea. BTW: Carb dip will destroy anything rubber in a carburetor so take care to only dip parts that are metal. It will also (generally) not clean internal passages; a welder's wire and compressed air and perhaps a can of spray cleaner will do the job. One issue with small engine carburetor is that if you remove the bowl, the oring that seals the bowl to body will often be distended and not want to return. Perhaps have a new bowl oring on hand. Lots of folks swear by Sea Foam products but I have not found any of them useful. Be it spray or stuff you pour in your gas. Stabil is what I use in my gas cans which I use to power my small engine stuff (lawn mower and lawn tractor).

Can't say I disagree about Chinese knock off carburetors but I always keep one or two spares in the even that the knock off carburetor on my old clunker riding mower has carb issues. Not really worth cleaning as they are less than $20 or so.

https://www.youtube.com/watch?v=L354qjss5Rg

[Raptor Dave]

Originally Posted by Don77

origanal post is sept 2022

LOL...gotta love it!

I belong to a couple forums where threads 10 yrs or older get resurrected.
Still good info sometimes come from them but it's still funny!

[JRTJH]

Originally Posted by Raptor Dave

LOL...gotta love it!

I belong to a couple forums where threads 10 yrs or older get resurrected.
Still good info sometimes come from them but it's still funny!

The date of the thread is the first thing I usually check... This time I hadn't and, well, once again, we're all reviewing a previous issue from some time ago... So, yep, we probably won't be "helping the OP", but...

It's still good information for someone with an Onan generator, or with a riding lawn mower that's been in storage over the winter.... Spring means lots of small engine equipment and every one of them has a carb to contend with....