Fuel Smell Ideas?

....I have encountered a very frustrating issue that has me completely baffled. I have been fighting this for some time now and finely decided to get to the bottom of it. When the canopy is closed, siting on the ground for any length of time I get an extremely strong accumulation of fuel fumes inside the plane. It doesn't matter if an hour or days it is the same. I installed wing root seals and boots and that did nothing. It is now to the point that I am very concerned when initially starting, that there is an explosion hazard. I always try to air it out first. I pressure checked the vent lines, fuel lines, fuel valve, replaced sender gaskets both sides, went ahead and replaced the fuel valve just because. I pressurized the fuel tanks with and without fuel. left the pressure on with fuel full for hours thinking perhaps, I will see something leaking. No luck! I am out of ideas and am frustrated. I need the FUEL FAIRY to find this one. If she can't I guess my only option is a bilge evacuation fan, like a boat! Ideas? Thanks, Allan

I have that problem usually once a year when either fuel tank float cover plate decides to spring a "weep". Usually shows up when the wx gets cold and all the aluminum shrinks. After a couple of weeks, some minor blue stains will show up along the bottom of the wingroot fairing. Usually the leak is around one of the 12 screws that hold the plate in place.

Allan
I know you replaced the fuel selector but all of my fuel selectors, on different planes, have sometimes leaked. The leak happens around the stem of the valve and it comes from the tank NOT in use.
If there is a bubble of fuel in your vent system it takes a bit of pressure to force air past this. This small amount of pressure is enough to let a bit weep around the valve stem. For me this happens after take off on full tanks on a sunny day. The sun heats the fuel in the OFF tank and it causes that bit of pressure around the valve stem. If I change tanks under 10 minutes of flight it does not happen.
Touch a piece of kleenex to the valve stem and see if it wicks blue.

I had fuel smell every time the electric boost pump was on in my 8. Lots of research later, I found two B-nuts that could take 1 more flat of tightening and that was enough to seal the connections. Now the smell is gone with pump on or off. Interesting it was not leaking enough to see any blue stains from the connections, but enough to smell.

My two sources of cabin fuel stink all fixed.

1. By the gascolator.





2. Weeping screws at the root of a tank. It will find the way to the cockpit and the boots can't stop it.





Let me know Alan if I qualify for Fuel Fairy

My guess is a tank leak too small for the fuel to make it to the dripping (blue staining) point. How long did you maintain pressure on your tanks, and was it with them completely empty?
I would open the wing inspection port and look down the back of the tank lip with a flashlight and mirror to see if there is staining there. It can sit on there and evaporate without showing an external stain. - At least on a 6. I assume the tank/spar configuration is similar on a 9.

Find the source

If you smell it that badly, something's leaking...Id fix it before flying again.

My friend had another airplane in his hangar and we kept smelling fuel. We were standing there looking at the airplane when a small weep became a flood of fuel about 1 inch deep in the cockpit.

Cm

I had the same problem. Make sure your B nuts are torqued around the fuel vent line. Once I took care of that the problem went away. Well until I filled the tank up to the BNC fitting and then the smell came back.

Just dealt with this issue on my 182, like Vlad mine was at the gascolator pass through on the firewall.

Ummm.... I'm rather fond of the smell of 100LL..... Reminds me of airplanes... ;-)

rv9av8tr said:

Ummm.... I'm rather fond of the smell of 100LL..... Reminds me of airplanes... ;-)

Click to expand...

Ha. I thought I liked it too, until I flew a few hours in a plane with a leaky fuel tank in the baggage compartment. The novelty wears off real quick.

This is the second time in as many weeks that someone has reported an issue with fuel smell in the cockpit. I don't have the silver bullet to your problem Allan but please ground your plane until you get the problem solved. If you smell fuel and its not coming out the overflow/vent tube, you have a serious problem that a bilge blower isn't going to fix.

Christopher Murphy said:

If you smell it that badly, something's leaking...Id fix it before flying again.

My friend had another airplane in his hangar and we kept smelling fuel. We were standing there looking at the airplane when a small weep became a flood of fuel about 1 inch deep in the cockpit.

Cm

Click to expand...

+1

A constant smell even after airing a bit won't usually come from invisible weeping. While you don't need a lot of fuel to create an odor, my experience is that a couple of barely visible drops cannot produce enough vapor to create a strong smell. Have you carefully examined the engine side of the firewall? I sit outside and have been working on stopping water invasion. Anything dripping down the firewall will work it's way into the gap between the firewall flange and lower skin and gravity brings it in to the cabin. This is where I would look next. Also look at fuel lines penetrating the f/w. A leak at a connection on the engine side can cause a drip into the cockpit if it slopes downward in the aft direction.

Larry

Get a detector

I had same issue, fuel smell when plane sat and I opened the canopy. I finally bought an Explosive Gas Detector.

Sniffed all around the cockpit nothing but it did detect gas, just no strongly. I moved to the wing root and if I put it up in the crack that leads to the back of the fuel tank it went bonkers.

Turns out a rivet on the back baffle of the tank had a leak(not my fault they are QB wings). At first it only left a smell not blue stain but by the time the smell was strong enough for me to get the detector it was leaving a very tiny blue stain at the attach seam on the bottom of the thank.

The detector is like this one, best $200 spent. I now use it every annual to check for slight leaks, none found so far.

http://www.amazon.com/gp/product/B000HHTY7Q/ref=pd_lpo_sbs_dp_ss_3?pf_rd_p=1944687722&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00628V0YO&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=1QXN0KYPJHEJ3VFT3290

Cheers

If you are using any flexible lines, don't assume they are not leaking. We had fuel smell in a Cessna that we assumed was a leaking fuel valve. It turned out to be a new SS braided fuel line.

Carl