Gasoline odor after generator is shut off

[mikervet]

I have a 2022 Tiffin 32SA. I bought the coach in August 2021. I have noticed a smell of gasoline after I run the gas generator and shut it off. It is an Onan 5500. I have noticed the smell since I got it. The smell dissipates after 5 or 10 minutes. I have followed the fuel line to the point it goes thru the frame to the gas tank and can not see any leaks. I had the coach at Tiffin last July and August 2022. The tech checked it and told me it was fine. He said it was gas evaporating from the carb after it was shut off. No odor when it is running. I have had 2 other motorhomes with generators and have never noticed gasoline odor after shutting down. Has anyone else noticed the odor on their motorhome after running their gasoline generator?

[Arch Hoagland]

I have an Onan 5500 I've been running for 19 years and haven't smelled any raw gas yet.

[PJStough]

With the generator running and the cover off, look for a cracked fitting just below the carburetor. I along with many others have had this problem. Luckily I discovered it by accident, instead of by the generator catching on fire.

[twinboat]

Thing that comes to mind is the anti-runon solenoid not shutting.

It's a needle valve that sits under the carb bowl and shuts the gas off from the main jet when you hit the stop switch.

If its not stopping the gas to the main jet, the engine will draw gas in while winding down and send unburnt gas out to the muffler, because there is no spark when in stop mode.

If you can disconnect the wire while it's running and it keeps running, it's not shutting the gas to the main jet off.

Item 30 in this diagram.

[bneumann]

Find a Cummins service dealer who should know best.

[TandW]

Originally Posted by twinboat

Thing that comes to mind is the anti-runon solenoid not shutting.

It's a needle valve that sits under the carb bowl and shuts the gas off from the main jet when you hit the stop switch.

If its not stopping the gas to the main jet, the engine will draw gas in while winding down and send unburnt gas out to the muffler, because there is no spark when in stop mode.

If you can disconnect the wire while it's running and it keeps running, it's not shutting the gas to the main jet off.

Item 30 in this diagram. Attachment 387813Attachment 387814

Exactly!

[JIMBO34PA]

When I first bought our 34PA i had raw fuel smell after shutdown. Turns out that I was holding the off button on dash till I heard generator shut off. Found out that when holding off button it primes the fuel system. So when shutting down press and release the off button not hold down.

[mikervet]

JIMBO34PA
You may have solved my problem because I do hold the off button until the generator shuts off completely. I will give it a try.

[Arch Hoagland]

mikervet...Let us know if that cures it.

I hold down on mine until it stops completely and never got the odor.

It seems to me if I didn't hold it down for a while the generator would continue running.

[sightseer 30B]

Mikervet - have you had a chance to try either of the above ideas? Stil having smell?

I have the after shut-off smell as well on a 2019 32sa. 98 hrs on generator. I thought I was holding the off button down myself, but still had the smell when ensuring that I only pressed the button momentarily. No odor when running. Only after generator stopped running.

I do see some vapor coming out of the carb throat after I shut it off with the air filter removed. I will try smelling the exhaust pipe outlet next time as well to see if fuel is being dumped there on shut-off as well.

[twinboat]

Originally Posted by Arch Hoagland

mikervet...Let us know if that cures it.

I hold down on mine until it stops completely and never got the odor.

It seems to me if I didn't hold it down for a while the generator would continue running.

Try just tapping the off switch and see what happens. Then maybe you'll be a believer.

[VetPartTimer]

Originally Posted by PJStough

With the generator running and the cover off, look for a cracked fitting just below the carburetor. I along with many others have had this problem. Luckily I discovered it by accident, instead of by the generator catching on fire.

I too am having this issue and am quite frustrated that I cannot find the source. Your response intrigues me.

Can you elaborate on this cracked fitting?

On the engine case?
On the carb itself? The float bowl? The solenoid?
Spacers/gaskets in either side of the carb?

[mikervet]

I did try JIMBO34PA's suggestion of just hitting stop and releasing when shutting gen down. There was a definite decrease in gasoline odor, but I want to repeat it several times before I decide. And yes it shut down fine without holding the button down.