172F fuel smell in cabin

172F fuel smell in cabin

I have a '65 172F that has a fuel smell in the cabin only when the tanks are greater than 1/2 full. The smell is strongest when manuevering. My A&P replaced a gasket on the filler neck (Pilot's side) and looked at the rubber hoses coming into the top of the cabin. He thought they looked good. No obvious leaks or staining, but then again this fuel evaporates quickly. Any advice will be appreciated.

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Re: 172F fuel smell in cabin

Check the filler neck where it is welded to the tank.
When the line guys allow the fuel nozzle to rest in the filler  without holding it a bending force is imposed on the weld, eventually causing it to crack.I would also check the fittings on the fuel lines for  cracked ferrules. You may also have a hole in the tank caused by abrasion between the tank and the wing structure. The only way to really know is to remove the tanks. Don't forget that the screws that attach the tank cover panels are structural and need to be replaced in kind.

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Re: 172F fuel smell in cabin

Curious about your fuel smell problem... Let the forum know what you find.

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Re: 172F fuel smell in cabin

Sure will, and thanks for the reply. I have a June annual, so it's on the list. I've heard horror stories of guys stripping a few nuts on these wing panels and not being able to easily repair them, and since it's structural it's a huge deal. Any advice on removing them would be appreciated. I plan to start soaking them in penetrating oil and hopefully they will come out with no damage. Thanks again.

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Re: 172F fuel smell in cabin

I'm sure there are many on this forum with much more experience than I.
that being said I'll add my two cents. I've found the key to removing screws is to not mess up the phillips head in the process. Start with a professional quality screwdriver with an unworn tip. Follow up by removing the paint in the phillips head. Get in a position where you can down load the screwdriver with your body weight and gently begin to turn. If the screw begins to turn, you're not home yet as the threaded portion below the nutplate may be corroded and can cause you misery as it is driven into the nutplate. If you can get a little clearance between the head of the screw and the wing panel, spritz the screw with penetrating oil and leave it for a day. On your return remove the screw the rest of the way.

If the screw shows any resistance to your initial attempt to remove it, DON"T tear out the head. Get a screw knocker which is a device which attaches to a rivet gun. It has a phillips head driver attached to a handle which is perpindicular to the driver. The way it works is that you impact the screw with the gun as you rotate the driver with the handle. The combination will loosen the most difficult screw.

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Re: 172F fuel smell in cabin

BP Blaster is a good penetrant, A speed handle with a ratchet head works well, As does a long screwdriver say 16" for torque.
A little Valve lapping compound on the screw driver head helps with friction to stop from stripping srew head.

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Re: 172F fuel smell in cabin

I found a leak in my 62 Skyhawk located at the fuel guage sending unit. Right below the nut is a phenolic washer were the fuel would weep out of. The only difference is, I didn't smell it in the cabin, but it did cause stains near the cabin at the wing root. My mechanic put a good coating of epoxy around the washer and that was over 18 years ago and it's been fine ever since.

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Re: 172F fuel smell in cabin

OK...finally...about 30 days before annual, I bought a good Klein screwdriver and backed each tank cover bolt (Pilot's side) out a turn or so and sprayed a little WD-40 on each of them, then tightened them back down. I went in for annual this week and the screws came out very easily. The problem was the vent fitting on the outboard side of the tank was very loose, as in 1/2 turn to tighten it. I haven't flown it yet, but the A&P was confident that was the problem as it was almost finger loose. I'll post again when I know for sure.
Thanks for all the good adavice, fellas.
Mike Sprow

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Re: 172F fuel smell in cabin

Well, I topped off the tanks Saturday and took off...not a hint of fuel smell so the loose vent was definitely the culprit...thanks again to you guys who gave suggestions. Safe skies to you all.

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