Onan geny spitting fuel out of carb vent

[trimster]

All of a sudden, our Onan 5500 geny is not starting. Pulled the cover and air cleaner to find that there was a lot of raw fuel in the airbox.

When I attempt a start (without priming) gas pulses out the hole in the upper left of the carb intake.

Any ideas why this might happen? and how to fix it? My first guess is a float stuck open (up), but I don't know how this engines carb works.

Thanks for the help.

[rickeieio]

Bob, I'd say you're on the right track.  I hsd ours apart a few months ago, but it may not be exactly the same as yours.

I'd take the float bowl off and see if the float and valve are actually working.  Could be a bit of crud on the needle, or a sunken float, or........

Been wondering how your truck issues have shaped up.  Get 'er all fixed?

[NeverEasy]

Be sure to check the oil level in the crankcase.  The float bowl overflow will also allow gas to flow into the intake manifold and then into one or both cylinder top ends and then leak past the rings into the crankcase.  If enough leaks into the cylinder, it will lock up the engine like a stuck piston.

 

[trimster]

Thanks.  Just changed the oil yesterday.  This starting problem began 2 days ago. 

I'll watch that.

First, pull the bowl.

[trimster]

2 hours ago, rickeieio said:

Bob, I'd say you're on the right track.  I hsd ours apart a few months ago, but it may not be exactly the same as yours.

I'd take the float bowl off and see if the float and valve are actually working.  Could be a bit of crud on the needle, or a sunken float, or........

Been wondering how your truck issues have shaped up.  Get 'er all fixed?

How does one get the bowl off? 

[Darryl&Rita]

47 minutes ago, trimster said:

How does one get the bowl off? 

Bottom of the bowl, there should be a hex head. Lefty loosey, carefully, as the bowl will follow it out, and down, Gas will spill, be ready with a rag, and shirt sleeves rolled up past the elbow.

[Wrknrvr]

   If it is a newer style generator then the hex head nut Darryl was referring to.

  May actually have a fuel solenoid sitting there. I do believe it unscrews from the base. Just like the nut would be on a old carburetor.

  What model generator do you have. With the model number that you have  you could lookup a new carb for it. If you can find a picture of one you could see if it has a solenoid on the bottom of the fuel bowl.

  

[trimster]

It does have the solenoid on the bottom.

[trimster]

Soooo, pulled the carb. Found the problem.  The float was ¾ full of fuel. Now the mystery.  How'd it get in there.

I can shake the float and nothing seeps out, anywhere. No signs of cracking. 

I drilled a really small hole in the top and shook the trapped fuel out. I'm sealing the hole with JB weld for plastic. And I'm ordering a new float.  Until it gets here, I will be up and running. 

 

[rickeieio]

Nailed it.  😁

Float could have a little crack which opens enough with altitude changes to let a little gas in.  You could turn this in to a science experiment, warm the float, submerge it in cold water, repeat until the float is half full.  Then out of the water, heat it up and see where the moisture comes back out.  Or just pitch it and get a new one.  One thing's for sure, that leak is still there.

[trimster]

Yup. It's the original 2013 float.  Never been serviced. Oil & filters service only.

Inside the carb was really clean. 325 hrs on the meter.

Getting new float. 

[rickeieio]

Ours was built into the unit back in 2008.  I have no service record from the previous owner, but it was serviced a couple months ago.  It'll get a workout at the Albuquerque Balloon Fiesta in a few weeks.

[trimster]

Albuquerque is where we bought our new (to us) 5th wheel 3 weeks ago.