Different Fuel Smell

[ArlingtonRV]

I recently smelled a rather strong fuel smell in the cabin. After checking the engine over and finding none of the usual causes for the smell I began to wonder if it was just running rich and I was smelling exhaust. Then I saw the stain on the belly of the fuselage. It started at one of the rivets and went pretty much right down the center. It was just behind the front seat bulkhead. What is located ubder the floor in that very location? The fuel shutoff valve. I pulled the floor panel off and sure enough there was fuel in there. I turned on the fuel pump and could see fuel dribbling out of the top fitting on the valve side.

The airplane has flown more than a year with over 125 hours on it with no problem. I just did the condition inspection in June and there was no sign of fuel around the valve. Whatever happened did so in the last 3 or 4 weeks. None of the fittings have moved and nothing is loose. My fear is that the valve itself is cracked.

Naturally, I found this after completely filling the fuel tank, so I have to defuel a full airplane to get the valve out. Since I will have the valve out I will put in a new one, even if I can't find anything wrong with the old one.

 

[N223JH]

You describe the leak position as the "top fitting on the valve side." If this is the pipe fitting you are referring to--as opposed to the "B" nut connection--you may have had the car gas dissolve the pipe thread sealant.

I experienced this after a few hours and subsequently discovered that my aircraft-grade pipe thread sealant was not compatible with car gas. Although Rotax and its accessories are designed for use with car gas, other components we customarily use on A/C may not be.

Because of the variety of car gas formulations, even products labeled, "For use with all types of gasoline, " may not be. Drop a sample of your thread sealant in a cup of car gas and see if a cloud forms.

Jim
#264 50 some-odd hours

 

[ArlingtonRV]

Great Idea

That's a great idea, thanks I'll give it a try.