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Fuel smell whilst flying

Hansgiant

Member
Anyone else had this situation :-

Over the last couple of flights I am sure that I can smell fuel.
Does anyone know where it could be coming from as I have inspected the tank and seen nothing.
The strange thing is that I can only smell fuel when flying and not when the aircraft is in the hangar.:confused::confused:

Any Ideas?
 
Many I see with fuel smells while flying have come from a leaking carb bowl. Check the drip tray or carb bowl bottom. This is fairly common.
The forced air coming into the cowl area forces the smell right into the cockpit.
 
In my case, it was a slightly loose connection to the electric fuel pump. I only smelled fuel when the boost pump was on during takeoff and landing. No dripping or blue stain. Just the odor.
 
We bad the same problem and could not find the cause.
Even took the tank out and repressure tested it. No leaks.
Turned out to be the hose clamps around the filler neck.
Like the carb air filters they tend to become loose as the rubber compresses in time.
The smell just came with a full tank during flight when the fuel is moving in and out if the neck.
Simple to solve but hard to find.
 
Anyone else had this situation :-

Over the last couple of flights I am sure that I can smell fuel.
Does anyone know where it could be coming from as I have inspected the tank and seen nothing.
The strange thing is that I can only smell fuel when flying and not when the aircraft is in the hangar.:confused::confused:

Any Ideas?

When I top off my RV8 there is a distinct fuel smell while taxing\takeoff, only happens when the tanks are topped off. Not sure if this is applicable to your situation?
 
I had fuel smell in the cockpit both airborne and while on the ground. Traced it to a leaking O ring on the fuel selector panel between my feet. Changed the O ring and smell disappeared.
 
Both my RV4 and RV6 have it

I have 2500 hours in these things and I have consistently got fuel smells occasionally while flying. Especially with topped off fuel tanks or in turbulence or aerobatics.

Where my smell comes from is the vent lines. The fuel splashes on the belly and the vapor gets sucked in where the flap push rods go through the belly. The vent lines get a little splash of fuel in them and the action in the fuel tank expands the vapor and pushes a drop out on to the under belly.

Steve
 
At my RV-12 I had a small leakage at the "red cube", I initially used the wrong sealant (corrected it with Loctite 567). Afterwards I smelled fuel during take-off but it turned out to be the fuel tester tube lying in the wind stream of the "airconditioning".
 
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Fuel vapors in the cockpit are not normal, and indicate a leak. I would trace the entire fuel system from tank to carb, looking for blue stains or wetting, especially at the joints. You can also try this with the fuel pump on to pressurize the system. If you have pipe threads anywhere, make sure you used sealant, or you will get slow leaks at some. Flared fittings are also known for slow leaks, so inspect those carefully for and blue dye.

Aaron
 
Thanks for all the advice. I guess I have my work cut out for me this weekend.

The most plausible suggestion is probably the connection between filler and tank as suggested here.
I will also check that there is perhaps not a float stuck in one of the carb bowls.

Many thanks again

I LOVE MY RV:rolleyes:
 
I also had a smell in my RV7 and it turned out to be a loose fitting on the loop of tank vent tubing inside the cockpit. Check those vent fittings for tightness.
 
Ok so I took off the engine cowl and checked both carbs for leaks- with the engine running. No visible leaks detected on the engine side. I did find the jubilee clamps on the fuel filler tube in the cabin to be a bit loose- so tightened them up.

I like the suggestion that perhaps the fuel tester, which I keep in the right hand pocket near the 'air conditioning' duct may be the culprit.
Thanks for that.

Cheers

Hans the Giant
 
Ok, I recently spent around 4.1 hours in the RV12.
I only smelt the fuel when pulling back on the throttle on decent when approaching the airfield to land or on decreasing speed in turbulence.

Any ideas? Perhaps the return to tank feed is leaking as the fuel demand is not as high?

Any suggestions would be helpful.

Hans Giant
 
If you are using 100LL you should see a blue stain if there is a leak. Auto gas of course would leave little if any evidence of a leak.
 
Hans,
Just to let you know I'm following this thread closely as I'm experiencing the same issues.
There is no evidence of fuel leaking inside the cowl or cabin so I guess its the gascolator next?
 
My guess would be - -

When pulling back on throttle, the engine can get into a fairly serious vibration, which I'd say causes the carbs to leak a bit during that time. You'd have to be really fast to take the cowl off and actually see residual fuel on the carb shields. High heat would evaporate it so quickly, you won't see it.
 
Ok, I recently spent around 4.1 hours in the RV12.
I only smelt the fuel when pulling back on the throttle on decent when approaching the airfield to land or on decreasing speed in turbulence.

Any ideas? Perhaps the return to tank feed is leaking as the fuel demand is not as high?

Any suggestions would be helpful.

Hans Giant

I occasionally get the same in my 6A. My tank vents receive ram-air while flying, so I concluded that the smell must be coming from the fuel tank vents as I slow down and relieve the pressure. When the tanks are full the vents spit fuel on the ground when the sun hits the wings, so there is no reason to believe it won't also happen in flight.
 
If you are using 100LL you should see a blue stain if there is a leak. Auto gas of course would leave little if any evidence of a leak.

Auto gas will leave a brown stain. The lighter components evaporate, leaving behind the heavier oils.

Have you looked under the baggage compartment floor in the area of the electric pump? Am doing my condition inspection this month, the skin under and downstream of the pump was stained brown. There was a drop of oil on the downstream fitting. A definitive leak. Was able to tighten the fitting a bit.

Should also look near the fuel flow transducer.
 
Exactly right Keith

Both my RV's with a total of 2400 hours have had the fuel splashing out the vents on the belly, then the fumes get sucked in the holes for the flap rods (slightly lower pressure in the cockpit). I get the smell with full fuel tanks on a hot day and during aerobatics. Occasionally it happens for no obvious reason. This has been happening occasionally for 2400 hours with both my 4 and my 6. I have just learned to live with it. It comes and goes quickly. It is part of my passenger briefing that they may have an occasional fuel smell.

Steve
 
Both my RV's with a total of 2400 hours have had the fuel splashing out the vents on the belly, then the fumes get sucked in the holes for the flap rods (slightly lower pressure in the cockpit). I get the smell with full fuel tanks on a hot day and during aerobatics. Occasionally it happens for no obvious reason. This has been happening occasionally for 2400 hours with both my 4 and my 6. I have just learned to live with it. It comes and goes quickly. It is part of my passenger briefing that they may have an occasional fuel smell.

Steve

yes agreed. unfortunately, many passengers equate fuel smell with carbon monoxide. if they only knew!
 
I found the source of my fuel smell. I did a short taxi today to move to a new hangar and on getting out I smelled the fuel when pushing the airplane and upon opening the oil door I saw fuel in the carb over flow line dripping out.
Next question is why and what can I do about it?
Roger you out there?
Thanks in advance.
 
I also get occasional fuel smell when the tanks are full. I switch tanks after ten minutes flight time to make room for expansion, usually this helps. Also I notice light fuel residue near the vents when tanks are full.

The smell might come in through the tail as well. During flight testing I checked for carbon monoxide. I got about 20 ppm during climb with rich mixture settings and higher AOAs. During cruise with lean mixture it was 0 ppm. A test pilot mentioned they get air from the tail into the cabin on their planes.
 
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