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RV-12 fuel odor

John Acardo

I'm New Here
RV-12 Fuel Odor

Initially when opening canopy, slight fuel odor?
Fuel cap vented and clear
No fuel leaks anywhere
Tank solid, no leaks
Once in the air no odor?
Normal situation with 12 and tank inside?

Thanks


Appreciate the feedback. Yes, very small leak from the sending unit.
Thank you!
 
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This will not be what you had hoped to hear...if you smell fuel it is leaking from somewhere.
I had the same experience with smell at opening that dissipated after airing out and in flight. Looked “everywhere“, no obvious leaks or stains. Disassembled, cleaned, and reassembled fuel connections with specified sealant on the “pipe” threads and STILL smelled fuel after canopy had been closed.
Finally found and traced a stain from the belly and center spar back up to a weeping screw on the sender plate. I had not seen it earlier because it was hiding behind the seat back and cross frame. “It’s always the last place you look”.
Good luck and have patience!
 
This will not be what you had hoped to hear...if you smell fuel it is leaking from somewhere.
I had the same experience with smell at opening that dissipated after airing out and in flight. Looked “everywhere“, no obvious leaks or stains. Disassembled, cleaned, and reassembled fuel connections with specified sealant on the “pipe” threads and STILL smelled fuel after canopy had been closed.
Finally found and traced a stain from the belly and center spar back up to a weeping screw on the sender plate. I had not seen it earlier because it was hiding behind the seat back and cross frame. “It’s always the last place you look”.
Good luck and have patience!

I am in process of doing my inspection and upon removing the backs for the seats, I too, found brown stains from running Mogas in the plane it's whole life on the front side of the tank, bottom 3 screws took about 45 to 60 degrees more turn snugging up on the Phillips pan head screws. Smell is now completely gone, I cleaned all the fuel stain up with Gojo brand hand cleaner. Builder bought the finished fuel tank from Van's.

Fuel smell was always very faint, upon opening up the canopy first thing in the hangar, and no longer around once engine was running.
 
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I too had fuel smell in the cockpit. When I did my first annual after purchasing the plane, I found weeps from the fuel tank. Again right around the sender plate. The previous owner used Ethanol fuel and I believe that compromised the fuel sealant. So I purchased a tank built by Vans. However during the inspection I also found a very small weep coming from the fuel flow meter. I removed it and put sealant on the fittings and reinstalled it. Again Ethanol eats sealant and that may have been the cause of that leak as well.

Keep looking. If you smell fuel it is leaking or weeping someplace.
 
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Ethanol eats sealant and that may have been the cause of that leak as well.

I'm curious why you think ProSeal is not compatible with ethanol?

ProSeal is a polysulfide-based compound that is resistant to a variety of corrosive substances, including oils, lubricants, gasoline, water, and alcohol.

Most everyone is using 93E10 in their 12's including me. If tank is sealed correctly it is impervious to mogas containing alcohol.
 
The only part of the system you can see without disassembly is four of the six tank sides. The outboard wall, bottom and fuel line hardware need you to remove the floor panels and inspection plates on the belly. Murphy would never let the leak be readily accessible for gooping with Pro-seal.
 
Fuel leaks... oh, I’ve dealt with so,so many of them.

The builder had installed the old acrylic fuel level window in the tank. It was leaking like a sieve when I bought the plane. Had to pull the top off the tank and completely re-seal it. Easy to find.

Then there was a weeping screw on the sending unit plate. Fixed that at the same time.

Then later a weeping rivet that was more difficult to find. I found it by putting paper towels in the suspect spots and waiting to find one damp. Fixed with a dab of tank sealant.

All was good for a year or more, then that little telltale whiff of gas. Seeping fitting at the fuel valve this time. They make little soft aluminum cone or cup shaped gaskets for those. Aircraft Spruce sells them, they’re cheap and they work.

All but the first two would have been much easier to find with dye and a UV light. The first two were quite obvious. If we have to chase down any more, that’s how I’m doing it.
 
My purchased flying plane developed the fuel smell pretty early in ownership. Lockwood suggested a Factory built replacement as less expensive and a better solution to chasing the leak.

Three years after factory built replacement a screw on the inspection plate began to leak. That screw was removed, resealed, and so far so good.
 
When building my tank my neighbor introduced me to "capped nut plates". He had a bunch so that's what I used for my 12. Sealed nicely and eliminates possibility of gas leaking through screw threads.

They are a bit expensive..about 5 bucks each. P/n NAS143A08
 
When building my tank my neighbor introduced me to "capped nut plates". He had a bunch so that's what I used for my 12. Sealed nicely and eliminates possibility of gas leaking through screw threads.

They are a bit expensive..about 5 bucks each. P/n NAS143A08

Did you mean NAS1473A08?
 
On my RV-12 build I chose to use only one capped nut plate on the fuel tank's forward access plate -- for the connection of the fuel gauge / fuel tank / airframe grounding wire.
 
The only part of the system you can see without disassembly is four of the six tank sides. The outboard wall, bottom and fuel line hardware need you to remove the floor panels and inspection plates on the belly. Murphy would never let the leak be readily accessible for gooping with Pro-seal.

Very true, and law of averages would say, leak is on hidden side of tank. So, if you have fuel odor you need to remove the tank to fully investigate where leak is. Do very thorough repair and leak test with 1psig and soapy water. Should be hunky-dory going forward.



you are my everything poem

 
Law of averages?
Jim, I think you mean "Murphy's law" which, in my experience, results in actual negative outcomes far in excess of any mathematically predicted average! ;)
 
I'm curious why you think ProSeal is not compatible with ethanol?

ProSeal is a polysulfide-based compound that is resistant to a variety of corrosive substances, including oils, lubricants, gasoline, water, and alcohol.

Most everyone is using 93E10 in their 12's including me. If tank is sealed correctly it is impervious to mogas containing alcohol.

First of all I am by no means an expert. I did attend the LSRM course at Rainbow early this year and we had a discussion on the corrosiveness of Ethanol. I know Vans has changed their sealant formula a couple of times over the years. Since the sealant must be mixed by the user, even a very slight change in the mixture could compromise the integrity of the sealant. Brian at Rainbow said he never likes to leave Ethanol sitting in tanks for that very reason. And considering how many folks on this thread and others have had leaks and weeps. I wouldn't say that all the tanks are impervious to Ethanol Mogas. Perhaps they are if the sealant is mixed correctly and the process is done perfectly but, really who is to say.

I am lucky I have non ethanol Mogas available readily at about 10 different gas stations near me.
 
UV Dye

Perhaps a question for Paul, but does anyone know if this UV dye will have any impact on the fuel system, engine performance, etc.? Is it safe to use? I get that people use it in cars and A/C systems, but curious if it would cause trouble for our finely tuned and tightly spec'ed engines. :)
 
I used the dye to track down my smell. It works good especially if you inspect at night with the black light. initially I was looking in the engine area for the leak and suspected carburetor gaskets. When I opened the bowls it went everywhere. It takes a bit of clean up with acetone before you can test again. To answer your question I did not drain the tank after testing and have run over 100 gallons since with no issues.
 
I used the dye to track down my smell. It works good especially if you inspect at night with the black light. initially I was looking in the engine area for the leak and suspected carburetor gaskets. When I opened the bowls it went everywhere. It takes a bit of clean up with acetone before you can test again. To answer your question I did not drain the tank after testing and have run over 100 gallons since with no issues.

Good to know... another 20 to 24 hours or more, no problems from the dye.
 
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