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Fuel Smell

I get a strong fuel odor when the tanks are 1/2 full or more and the canopy closed with the airplane left in the hangar. I get the odor as soon as I open the canopy. I have checked all the fuel lines and the tanks and haven’t found any leaks. Any ideas?
 
I would be checking the vent lines as well. They have multiple connections inside the cabin and the fitting inside the tank won't see fuel until around half full.
 
End of flight smell

It might be worthwhile to put a wrench on all of them. I had a similar trend appear at about 75 hours out of nowhere. I would only get a smell at the end of flight taxi, less than 10g/side. Nothing was loose, but I loosened them all and retorqued them, fuel and vent. I suspect it was a vent, but no real indicators existed (staining, sniff test) on any of them. Fixed it. I’ve been taking more care with fuel selector during condition, I might have been a little rough with it in the past, but I’ve got flightline flexible to and from. I added clean cloth fitting wipe down to my condition inspection checklist as a precaution.
 
If you do smell fume, specially when on the ground, then there is an issue some where. often it take a bit of time to find it but those who have smelled fumes and kept on looking, finally find it.
Ask me how I know that.

The suggestion of vent line is a good start but I think you will need more than half a tank unless your B nut for the vent line inside the tank is lose which it is a very possibility.
 
Go under EVERY fitting with your finger or a clean white paper/cotton towel. You will find somewhere green/blue residue ... then follow that. I had the same ... but went flying twice, until I looked it over. If there is a fuel smell, then you have a leak.

Check it prior the next flight, don't risk anything!
 
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I had a similar problem. Checked every nut on fuel lines in the cockpit (old style Fuel Inj. boost pump). Had a small leak at the firewall pass-through fitting, but fixing that didn't solve the problem. Turns out the rubber gasket under the fuel sender on the tank was going bad. The fuel smell came through the wing/fuselage holes. Removed the gasket and prosealed the sender to the tank. No more fuel smell.
 
It is amazing how such a small fuel leak can lead to fumes you can smell. After fuel testing I could smell fumes in my cockpit and went on the hunt to find it. It took multiple attempts but I finally found a small drip on one of the factory connections on my boost pump. The dye will concentrate even under the smallest of leaks.
 
fuel dye

I used some fluorescent fuel dye to try to track down a slight fuel smell, and realized that unfortunately Loctite 561 thread sealant stick is also fluorescent. BTW, so are the plastic inserts on locknuts, and my thread sealer, but that's another matter.

Trying to track down a very slight fuel smell is harder than it sounds.

IMG_2332.jpg
 
A leak along the back of the tank will eventually enter the cabin via the spar. Ask me how I know...

My left tank had a slow leak when built. I typically left the tank less than 1/2 full to avoid the leak. One day, I started after the tank had been filled higher than 1/2 for a while. The engine lit off and, as I taxied out, I noticed a smoky haze in the cockpit. Back to the hangar and saw nothing unusual. A couple weeks later, upon pulling the upper intersection fairing, I noticed some black soot at the gear leg. I had been on fire for a few seconds :eek:
 
I used some fluorescent fuel dye to try to track down a slight fuel smell, and realized that unfortunately Loctite 561 thread sealant stick is also fluorescent. BTW, so are the plastic inserts on locknuts, and my thread sealer, but that's another matter.

Trying to track down a very slight fuel smell is harder than it sounds.

View attachment 5292

So don't leave us hanging...did that technique ultimately work, after you ignored the nylocks and torque seal? :) And let's see a picture of the leak under UV, if it did work!
 
So don't leave us hanging...did that technique ultimately work, after you ignored the nylocks and torque seal? :) And let's see a picture of the leak under UV, if it did work!

I called Tony, he said the leak was one of the pipe thread fittings coming out of the red cube. Looks like the cube was mounted between the pedals from the pictures he sent me.
 
So don't leave us hanging...did that technique ultimately work, after you ignored the nylocks and torque seal? :) And let's see a picture of the leak under UV, if it did work!
It did not work for me - I suspect that the leak is under the wing root fairings. Need a rainy/foggy weekend to remove those. I'll get some pictures to try to close the loop - hopefully that's where I'll find it, or perhaps the external part of the fuel vents.
 
A few years back I chased a fuel leak / cockpit smell for months in a Pitts I had at the time.

It turned out to be a piece of stainless braided hose that had hardened & cracked internally.... when the fuel leaked it wicked along the braid and evaporated over a long stretch without leaving any localized blue residue. I only found it in the end when it turned into a "gusher" :eek:

Only PTFE lined hose for me since !
 
I called Tony, he said the leak was one of the pipe thread fittings coming out of the red cube.

I had the same problem ... even though the fitting had good fuel lube and was torqued in place. 45 hours new. No blue residue that I could find, but the leak only showed up when system was pressurized by the boost pump. I noticed the smell only on takeoff when the pump was on.
 
Fuel smell .. no sign of a leak ?

Ok...

I just was fighting the same issue ..

Fuel smell in the cabin ..

Sill there the next day ...

Can’t find a leak anywhere !

Then looking to my right during flight...

See tiny .. tiny ... fuel leakage from cap .. tiny ...

Never any sign of it on wing..

Did the magic with fuel cap ( tighten it up a bit)

Fixed!

Never connected the two till after a few flights and noticed no more fuel smell in cabin ..

Check the fuel tank caps...
 
I had the same problem ... even though the fitting had good fuel lube and was torqued in place. 45 hours new. No blue residue that I could find, but the leak only showed up when system was pressurized by the boost pump. I noticed the smell only on takeoff when the pump was on.

I don’t think “fuel lube” is a good sealant.. I started using Locktite 567. It’s a white paste like the Teflon pasted that I used to use from permatex. I believe “Fuel Lube” is a lubricant, used for o-rings and valves.
 
Fuel Lube is a lube for O-Rings and gaskets. It will be tight for a while, but then start to leak.

Use one of these Loctites: 565/567/577
 
I don’t think “fuel lube” is a good sealant.. I started using Locktite 567. It’s a white paste like the Teflon pasted that I used to use from permatex. I believe “Fuel Lube” is a lubricant, used for o-rings and valves.

Same experience years ago. Locktite 567 is my go-to sealant.
 
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