Smell of fuel during rapid descent.

[Jcurry]

Hello,
I have a 912 ULS. I have noticed that when I'm at 3500 feet or higher and I pull the throttle back (mid 4000 rpms or lower. "Chop and drop") and shove the nose over for a rapid descent (to get below a cloud deck for example) I will get a whiff of fuel. This does not happen if I descend with power at 4500 rpms or higher. I don't like to "chop and drop" and I try to avoid doing it.
1. Where is the fuel coming from? Vent line? Air filter?
2. Why am I getting a fuel smell under the above mentioned conditions? Does the carb fuel bowl flood with a rapid reduction of throttle?

Thanks,
Jack

 

[FORANE]

Descent causes a relative increase in outside the cabin air pressure. Air will flow into the cabin from areas such as wing roots. If you have a very slow leak at say a fuel line connection to wing tank, it will show up as a fuel odor on descent.

 

[cactusman]

There was a thread on here about the new tank vent set up and making sure the T-loop flexible tubing tank vent was set up correctly. I had an intermittent smell and corrected the loop and it seems to have gone away.

Other possibilities might be negative g on the carb floats possibly and some overflow from the carb bowls?

 

[DHeal]

Also, getting a whiff of fuel can be a sign that your carb is venting due to overweight carb bowl floats or a worn float needle valve. In my experience such an event usually occurred during climb-out but it may occur in other flight conditions as well. It is easy enough to check the weights of the two pairs of floats.