5500 Onan starts then dies, help please

[RV-1_2n-FUN]

2008 Onan 5500 that I neglected and did not run every month with load since May. Using start switch on the generator, first priming then start the gen. It starts and runs ONLY as long as I hold almost completely closed the butterfly under air filter. If I take pressure off the B-fly opens wide and sounds like gulping air then shuts down with code flashing 36. Reset code, prime and start up and again runs only by holding closed the butterfly. Sprayed plenty of Seafoam in to no avail.

Any ideas of problem???

TIA

[Cummins12V98]

If you can stick with non Ethanol Gas there is no reason to add anything. I run whatever is cheapest during the summer in my boat. When it gets time to store for the winter I run each tank dry and refill with non Ethanol. I let it set for the winter without running carb dry and come Spring it fires right up and runs great with 6 month old fuel.

[TomD62]

What really gums up and corrodes the internals of carburetors is the Ethanol in most 'gas' . Ethanol attracts water from the humidity in the air and it turns the gas and other additives into a corrosive stew. It's not as bad in fuel injection systems because they are sealed, but carburetors are open to outside air.
At the end of your travel season, run down to the bottom of the tank, then add fuel stabilizer and 100% gas that some stations sell, run the generator for a little bit to pull that into the lines. When you shut it down, try to drain the carburetor bowl and incoming fuel line if you not going to be able to run it every 30days.

[Dirtclods]

Fisherman wrote:
Octane has absolutely no effect on the amount of crud building up in a fuel system.

Lower grad fuels have more c r a p the build in the carbs. That will clog the main jet.

[TomD62]

Sounds like it's not getting enough fuel.
Check the filter at the carb, is it clogged?
Also run it and then let it quit, then take off the bowl on the bottom of the carb, it it empty or full of gas, should be full.
IIRC, there may be a solenoid on the bottom of the bowl to let gas into the main jet, that's electrically actuated. You may use a trouble-light to check it.
Check to see you fuel pump is working, remove the fuel line from the filter at the carb and put a bit of hose on it to let it drain into a can or something (instead of spraying gas all over) and try to start it, do you get a good flow of gas ?
BTW , Seafoam won't clean anything, it's more of a lubricant. Use Berryman's B12, that will dissolve varnish, pull the air filter and spray some into every tiny hole you can see in the intake. Best to remove that carb and take it apart and spray out all the passages, but that's only after all else fails. Wear gloves and glasses, B12 is nasty stuff on skin and eyes.

[RV-1_2n-FUN]

Following a Long PRIMING today I pushed *start* and it fired right up. A couple of little hick-ups and I chose to hold the butterfly 1/4 open for an extended time, as in 5+ minutes as it continued to run fairly smoothly. Took CARB CLEANER and sprayed it in until almost dying, stopped and let it get back to idle. A few more sprayings and let it run until nice a warm then flipped the 2 breakers and 50AMP SERVICE resulted. Another 10 minute idle then both roof air conditioners PLUS water heater PLUS fridge with 30amps showing and RUN IT DID!!!

THANKS AGAIN and another check-out tomorrow hopefully will turn out OK.

[Dusty_R]

Just a thought.
Maybe the electric fuel pump stops when the generator starts.

[2112]

Did you replace the fuel filter?

[Skibane]

It really sounds like you were on the right track with cleaning the carb, but didn't go far enough.

Did you thoroughly clean the small passages? Typically, it takes a piece of small-diameter wire to rod them out.

Also, Sea Foam is not a particularly good substitute for carb cleaner.

[RV-1_2n-FUN]

Generator starts better than before then only runs for 4 minutes and dies. Checked pump with hose disconnected and pressure seems good so totally flustered and figure it's time for $$$$ and a pro.

[RV-1_2n-FUN]

Broke down the carb today and the inside looked as clean as the day it was assembled. Didn't have any cleaner so put Seafoam through everything then reassembled and WHAM-BAM it ran but only for 5 minutes.

Same as before r.e.-shutting down, so held butterfly and it ran great.

THANKS for the replies.

[wa8yxm]

You sprayed seafoam into the throat of the Carb.
But from your description I'd say it needs carb cleaned.
it is SLIGHTLY possible that adding seafoam to the tank might help
But I think Disassembly and cleaning is in order.

NOTE: This is not the only possible issue.

[Fisherman]

Octane has absolutely no effect on the amount of crud building up in a fuel system.

[Dirtclods]

Seafoam is a fuel treatment it doesn't work well after a problem exist. You gotta have in the tank and if your running lower octane fuels you'll get more **** built up in the carb.

[dougrainer]

A1B00902 wrote:
check the oil level, Onan will not run if low on oil

True, but holding the choke butterfly would not override the oil pressure LOPKO. Doug