Strong Fuel Smell

[Gus Ziegler]

Hello

I am renting a 1966 PA-24-260B in southern California. It is in nice condition with older radio's.

All Comanche's that I have flown over the last 30year have some fuel smell in the cabin. However this one gets worse after landing during taxi into the ramp. Anyone know how to fix this or what the problem may be?

Thank you
Gus Ziegler

[Charles Schefer]

Most likely fuel bladders needing replacement. Over time they dry out and crack especially at the top and especially if the tanks are not kept full when the plane is sitting. The most common place, especially for a plane that is kept outdoors is the right main tank. The black pilot wing walk absorbs more solar heat and accelerates the deterioration of the upper part of the tank. You smell the fuel during landing because on landing the fuel sloshes around and some weeps out of the top. The wheel wells run at positive air pressure during flight so air is forced thru the inside of the wing in all directions including into the cabin.

- Charles

[N3322G]

Gus, ditto what Charles said.

After we replaced the bladders in the Twin, ta-da, no fuel smell. If the 260's are original be prepared to replace any connecting hoses and screens. Be sure to replace the bladder access gaskets.

You might also look closely at the bottom of the wing roots for possible blue fuel stains and fuel will sometimes run across the top, down the side to this area.

[Gus Ziegler]

Thanks Guys

I flew the airplane on 7th of Jan and all tanks were filled and then the aircraft was parked till 12th. During my pre-flight (on 12th) I opened all fuel caps and found all four tanks to be very full. There is no evidence of a fuel leak.

I am puzzled with this smell as it is very strong.

Thanks
Gus

[Kristin Winter]

It only takes a few tablespoons, usually leaking out of the top of the tank, and not the bottom. Look for stains under the wing first. If you find some along the spar rivets on the lower skin, it is likely the aux tank. To check the main, remove the after most wing/fuselage fairing and feel under and aft of the main tank nipple and line where it comes out of the butt rib. If it is sticky, the main is leaking.

[Ed Asmus]

Two thoughts: I just had the right bladder replaced (left replaced 5 years ago) on the 1959 PA24 250 I fly and the bladder was leaking enough from the top that after sitting a few weeks, the fuel level was noticeably lower upon opening the cap and looking in the tank. This was the only evidence of a problem. No fuel staining anywhere and no oder. Apparently the fuel would evaporate before it made it to the bottom of the wing. Bladder replaced, problem solved. The bladder was original on that side and looked in very good shape upon removal surprisingly. The disappearing fuel developed over a period of only a few months. Once the bladder started leaking, it progressed rather rapidly. Started with a slight amount disappearing in a few weeks to about a gallon in about 2 weeks. After the level got down about 2 gallons, it would stay there.

Another possibility which I also experienced is a leaky fuel valve on the floor that can also be the culprit. Something else to check.

Keep us posted.

Ed

[Gus Ziegler]

Hello All,

I flew the Comanche again today and again found all four fuel tank very full. Also, no evidence of fuel stains on the bottom side of the aircraft.

Anyone ever hear of a problem with the fuel vent system on the Comanche?

Thanks Again
Gus

[Mark Anderson]

Gus,

I recently had a fuel smell and it was the fuel strainer. There were no signs of leaking fuel on the belly or the ground. It was leaking inside the wing/ fuselage cavity. The strainer can easily be rebuilt by replying the seals. One other time I had a fuel smell it was a lose connection on a bladder nipple.

Mark

[greg]

Check the fuel line connections at the fuel tank selector in the cabin. I had a small leak that I smelled only when taxiing after landing. It was a very slight leak and the area was not wet. It was discovered because of the small blue fuel stain. A little baby powder was used to find the exact location.

[Randy Johnson]

As a side bar...I've found that turning the fuel valve to the off position when in the hangar made a big difference in the cockpit when I returned to fly again. It's actually part of the checklist in some versions.

[Mark Anderson]

Gus,

It could be as simple as a fuel cap not sealing good and fuel sloshing up through the cap. I recently had this problem with smelling fuel only after landing with full main tanks. Each time I checked the right main fuel cap and it was wet with fuel around the cap under the fuel door. I replaced the cap and it fixed the problem. Also the fuel guy may be over filling the tanks and making it worse. Although I have never smelled fuel inflight.

Randy,

Personally I never turn the fuel to the off position. Once after an annual inspection I taxied all the way to the end of the runway, did the run up, looked down and the fuel was selector was in the off position. I don't trust myself enough to leave it off. Just my 2 cents!

Mark

[Randy Johnson]

I hear you Mark. Just one more thing to go wrong.

I use the old GUMP check religiously and it's saved me more than once. Under G for "gas" I check Both the fuel selector settings and the fuel gauge. Both will remind me if I'm fuel selector off. Also did a test to see how long it took to run dry with the selector off...in my carb engine it was never over 50 seconds.

Because the fuel system on our planes is, in my opinion, the least forgiving of all... it requires a fail safe approach.

Turning the selector off has eliminated the fumes in the hangar and the cockpit for me. But hey, if you don't turn it off it can't bite you either.

[Christopher Cotton]

[Roderick Tatchio]

I did a BFR with a good friend instructor a week ago. All tanks were full to the bottom of the ring . I was told that the tank is full to the bottom of the holes in the ring. I recieved 4 new gas caps for Xmas last year. The BFR included standard rate 180 and steep 180 turns. After the turns during the flight we both smelled fuel. I had experienced fuel smell after landing in the past but never felt uncomfortable about it. After the flight and shut down, fuel leaked out at the wing to fuselage farring on both sides and made a spot on the ramp about 8" dia before it stopped. I have been a part owner in this plane since 1991 and I do recall having the bladders remanned in the first year after the plane was purchased.
There is no fuel smell or evidence of leaking in the hangar.
The questions I have are as follows:
How do you determine if a bladder is leaking or which one it is.
Is there any safety issues if the bladder is leaking?
How long should a bladder last if the tanks are kept properly full.
What is considered properly full.