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  #1  
Old 09-05-2011, 06:10 PM
prkaye prkaye is offline
 
Join Date: Jun 2006
Location: Ottawa, Ontario, Canada
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Default strong gas smell with V-Power

Today I was at a small airport and at the gas pumps they had both 100LL and V-Power (91 Octane auto gas by shell with no ethanol). I decided to try the V-Power, and i filled my right tank, which only had a small amount of 100LL left in it. It ran fine and i burned through most of it this afternoon, but i immediately got a very strong smell of the gas in the cockpit when i started taxiing with it. It subsided a bit at high power, but when i throttled back for approach it came back strongly again. The V-Power gas is much more smelly than avgas.

I?m now grounding the airplane till I can figure this out. I recently sealed-up the firewall really well, so it?s gotta be coming from somewhere further back. But I?ve never seen a hint of liquid gas in the cockpit, so it?s a bit of a mystery. Is it possible to get a vapourized fuel leak through one of hte fittings in the cockpit which would give the strong smell without leading to pooling liquid gas?

Any suggestions or tips on how to diagnose this would be much appreciated...
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  #2  
Old 09-05-2011, 06:23 PM
rv9aviator rv9aviator is offline
 
Join Date: Jan 2005
Location: Arkansas
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I hope you find the problem. I have a little of the same problem with autofuel. I am assuming it is in the vent tube fittings. I hate smelling gas in the cockpit. I kind of wish I had installed the Rocket type coil vents. Keep us posted.
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  #3  
Old 09-05-2011, 06:25 PM
Danny7 Danny7 is offline
 
Join Date: May 2008
Location: central oregon
Posts: 1,089
Default gas leak detector

I wonder if something like this http://www.amazon.com/General-Tools-.../dp/B001TON9KE
would detect a gas leak fairly well? it shows detection for propane and methane in the description, i wonder if gas would have similar enough chemistry to detect?
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  #4  
Old 09-05-2011, 06:50 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
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Check your fuel vents and the plumbing leading to them. Autogas typically has higher vapor pressure than avgas, which might explain an unusual amount of venting from your aircraft. That vapor could be exausting from your fuel vents or from a leak in the fuel vent plumbing in the cabin of your airplane.
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  #5  
Old 09-05-2011, 07:07 PM
molson309 molson309 is offline
 
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Location: Longmont, CO
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My Rocket has double loops of tubing leading to a under-the-wing vent. All connections are tight. If I fill the tanks beyond a certain point (about 1 to 1-1/2 inches below the filler neck) I will get a strong odor of avgas in the cockpit when taxiing or after leveling off after climbing. If I fill it full and let it sit in the sun an impressive amount of gas will spurt from the vents. Once a couple of gallons have been burned off both tanks the odor goes away. It's coming from the vents.

On my RV-7A I routed the vent lines as detailed by Vans. Originally the "B" nut on one of the vent fittings (the flared connection in the cockpit from the vent fitting to the vent tube) was loose. This caused quite a odor of gas in the cockpit but never any blue stains. I found this by accident and once I tightened it the odor went away.

Auto gas has a higher vapor pressure combined with a much stronger odor. Any venting of fuel in taxiing or flight will most likely be quite pungent. One thing to check is whether this abates once the fuel level in the tank is lowered.

Mark Olson RV-7A F1-EVO Rocket
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  #6  
Old 09-05-2011, 07:11 PM
markscogg markscogg is offline
 
Join Date: Mar 2005
Location: Charlotte, NC
Posts: 306
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Auto gas stinks.
Try draining the auto fuel and replacing with 100LL.
Your problem may go away when all of the auto gas is purged from the system.
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  #7  
Old 09-06-2011, 08:43 AM
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n82rb n82rb is offline
 
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Location: fort myers fl
Posts: 949
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I would bet that detector uses a sensor from figaro sensors. I just checked their data sheets and the lp sensor has no data for gasoline. I would bet that it would sense it, but at a concentration probably higher than the human nose could sense.

bob burns
N82RB
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  #8  
Old 09-06-2011, 08:45 AM
prkaye prkaye is offline
 
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Location: Ottawa, Ontario, Canada
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Default

Quote:
Try draining the auto fuel and replacing with 100LL.
Your problem may go away
That reminds me of the story of the man who went to the doctor and said "my arm hurts when I raise it up" and the doctor replied, "well don't raise it up".

Indeed I don't get the smell with 100LL. But I attribute that to the fact that I just don't smell the 100LL. The autogas has helped me identify a problem that was previously undetectable. Rather than ignore it, I'd like to find and fix it.

The first thing I will check is those vent lines. I have the stainless steel bonaco lines (even for the vent lines), so I doubt the lines themselves are leaking, but maybe it is vapour pressure seeping through the threads of the nuts on the fittings. I could tighten these, and perhaps gob some RTV around the fittings to? The vent lines aren't meant to carry fluid (correct?) so there would be no harm in gobbing RTV over the nuts to help seal them up better?
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  #9  
Old 09-06-2011, 08:51 AM
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Jamie Jamie is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by prkaye View Post
I could tighten these, and perhaps gob some RTV around the fittings to?
I wouldn't do that, although it would be a good indicator as to where it is leaking since fuel breaks down RTV. As a general rule of thumb RTV should never be used on anything that ever touches fuel.
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  #10  
Old 09-06-2011, 09:07 AM
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John Clark John Clark is offline
 
Join Date: May 2005
Location: Santa Barbara, CA
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Quote:
Originally Posted by prkaye View Post
I could tighten these, and perhaps gob some RTV around the fittings to? The vent lines aren't meant to carry fluid (correct?) so there would be no harm in gobbing RTV over the nuts to help seal them up better?
RTV is the wrong thing to use anywhere around gasoline. It softens and expands, making it useless as a sealant and downright dangerous if it gets inside the system. Properly installed, the fittings will seal without "gobbing" anything.

John Clark ATP, CFI

FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
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