Smell of fuel

Fuel tanks, systems and parts
flyingfool
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Smell of fuel

Post by flyingfool »

Every now and again, when flying my A-65 Chief, I get a wiff of gas. I use autofuel so it is fairly distinctive.

I have recently replaced my copper fuel line between the aux tank fuel gauge and the main tank. I also have installed a new copper line between the primer and the tank.

I had for weeks checked for leaks at the connections of all the connections of the replaced lines and f ound none. I have put my hand on the primer line and the other connections and can not detect a smell or determine where this might be coming from. I also touched the main fuel gauge to see if it is weeping. Does not seem to be!

Could I possibly be smelling the exhaust while flying with the window open and the eye vent facing forward?

I do not notice it all the time only once and awhile. I admit it could all be in my head and my paranoid imagination. I do not get any sense of fuel smell in the cockpit after not flying for several days. Although I do leave the side windows open while it is not flying sitting in the hangar. What kind of extremely minor fuel leak would only occur when flying and not noticed while static?

Can somebody give me any suggestions where else I might look or if anyone else has the same thing happen to them?

Thanks
Dennis
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Post by Dennis »

Just a guess but since you can not find a leak, maybe the fuel level indicator is not sealed very well and is allowing fumes to escape.

Dennis
Last edited by Dennis on Wed Jul 22, 2009 17:10, edited 1 time in total.
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joea
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Post by joea »

Put some 100LL in from time to time. The dye in the Avfuel might help you find out where its coming from.
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Nathan K. Hammond
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Post by Nathan K. Hammond »

I would be suspicious of the main fuel gauge. I could smell gas on mine when the tank was full or close to it only. There was no indication (dye) of a leak, but after making a new gasket I never had the smell again.

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Post by gusc »

I had the same smell this past Sun and when I finally found gas on my right knee I decided it was the primer connection!!

I tightened it once but it started leaking again, tightened it again and it appears to have stopped.

The primer line will leak only when the fuel valve is on, this could confuse matters a bit.

To me, exhaust odor is nothing like raw gas.
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Post by joea »

Remember that primer line is in many cases old copper line, and work hardens. Tightening it may stop it now but it could crack and break later.

If its coming from the primer might take a look at replacing the lines for safety reasons. Last thing you need is an open fuel line in the cockpit.
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Post by DC Krog »

I would like to bet that the primer o-rings are shot due the fact that your auto fuel (which more than likely) has ethonol (sp.) and destroyed the material of the orings. Auto fuel likes to seep through all connections so if you choose to use auto gas I recommend using Fuel Lube on all fittings to prevent this from happening. Fuel lube is like bee wax and seals all fitting connections and it will not break down from gasoline. Works great.

Another problem might be the fuel gauge gasket (again the auto gas will seep through the gasket when sloshed around) use some fuel lube on the gasket.

You noticed Aeronca never installed an ashtray in the Champ and for good reason.
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Post by joea »

DC Krog wrote: You noticed Aeronca never installed an ashtray in the Champ and for good reason.
Every Chief and Sedan have an ashtray. Holds extra bulbs very well in my plane.
flyingfool
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Post by flyingfool »

Thanks for the responses guys.

I totally replaced my primer line about 25 hours ago with new copper line.

I used fuel lube (EZ turn) on the primer seals. My primer had the what I assume to be original leather seals. Not rubber type O-rnigs. So I coated them fairly liberally with the fuel lube and reinserted. Works nice and smooth. My thought being that the fuel lube would help provide a good suction seal with the walls of the tube.

I have noticed when priming that it seems to make a different noise and may take a bit more "pumps" to get what I feel is fuel into the primer "stem/resoviour". So maybe I have a small leak in this conection. Not enough to drip or otherwise become obvious.

I also shut my fuel valve off every time. I do not understand why the fuel valve has any effect on the primer. Because at least on my Chief, the primer line comes from a "Tee" connection from the left hand main fuel tank connection where the aux tank drains into the tank, not a Tee at the main fuel valve connection.

personally, I do not like the way the Chiefs aux tank system is set up. I would rather they would have installed a nearly duplicate fuel valve for the aux tank as the main fuel tank valve rather than the side valve.

I think I may take a twist on each of the primer lines compression fittings. Just a little more tighter. It may be just slightly leaking.

JoeA. I like the idea of using straight 100LL for a dye test. I currently use 25% 100LL and 75% autofuel. And I verify that the auto fuel is completely ethanol free. At least for the time being!

I have put my fingers around the main fuel gauge and do not notice any smell transferring to my hands. I will ahve to try to keep mental track WHEN or what conditions I notice this smell. For example is it only during a climb and/or with the fuel tank nearly full? Or any condition. If in a climb then the guel gauge is suspect. If all the time then the primer or something else would be more likely.
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Post by gusc »

Joe,

A new primer line connection is on my list of things to do!

DC,

If you get fuel lube into the primer line it will never come out and probably is partially blocking the line.

ff,

If there is even the slightest seepage you will have fuel on your hands!

I wish my Champ had an ash tray, they are very handy. However, never, ever smoke in a fabric airplane. There is nothing like dropping a burning cigarette down into the fabric belly!!
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DC Krog
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Post by DC Krog »

For the record I never said to put Fuel Lube on the o-rings of the primer I said the line connections. You souldn't apply anything to the o-rings of the the fuel line primer. Maybe some light engine oil when you first install the plunger.

Second the Ashtray statement applied to Champs and not the "luxury" model Chief. Did they have curtains and draps in Chiefs. They are too fancy for me....

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Re: Smell of fuel

Post by Holcombe »

I get the ocasional fuel smell and currently think it is a combination of full tanks and rough air or handling. The overflow from the wing tank is right next to te leaky door seal where rain comes in if I fly through any, and if I slosh fuel out there that would cause the problem.
Tail winds are a "Good Thing"
flyingfool
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Re: Smell of fuel

Post by flyingfool »

I may have found the culprit.

I have noticed that when I pull out the primer, the stem smells of fuel. So I think all I'm smelling is the remnants of that fuel drying off.
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joea
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Re: Smell of fuel

Post by joea »

Get some AN fittings and block off the primer and see what happens.

Also it might be leaking internally into the engine, causing it to run rich.
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Re: Smell of fuel

Post by jc pacquin »

I filled the champ up one day, took off and smelled gas. Then I SAW gas. I had filled the tank right to the brim and in a steep climb the fuel gage leaked. I never filled it that full again and it never did it again.JP
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