National Aeronca Association Bulletin Board

There should be no fuel on the primer pump when you pull it out, this shows that your O ring is not wiping the fuel off. Time for a new ring.

I found air and bubbles forming at the lower front center of the windshield when I got caught in a little rain last summer. That is right behind the Gas cap. So if there was any fuel sloshing up and around the cap while in flight, it would certainly come in there. Probably where the smell comes from. I'm guessing that the cap doesn't always get put on 100% right and from time to time can cause the gas smell in the cockpit.

Two more places to look are the aux fuel valve and the aux fuel tank overflow. If your Chief still has the side panels in the cabin, the aux fuel valve might be seeping and be unnoticed behind the side panel. The seep may even be intermittent with movements of the valve.
With the aux fuel tank overflow hidden behind the headliner and baggage compartment, deterioration of the rubber hose connection at the tank might go unnoticed. Bumpy air with fuel sloshing in the tank could cause a seep there. jrh

I'm also having fuel odor problems in the cockpit of my 7 AC/DC, especially when I fill the tank.

I have replaced the gasket of the fuel gauge and don't smell gas there. I've checked the other usual suspects - fuel valve and plumbing, primer and wing tank plumbing. The problem seems worst when the main tank is full. Another possibility I haven't checked yet is a crack where the filler neck joins the tank.

I did notice the bottom edge of the windscreen at the cowling is not sealed well. There is a riveted strip of aluminum that secures the windscreen to the cowl and it has old, pealed silicone sealant with gaps. I believe outside air leaks into the cockpit at the bottom edge of the windscreen from right behind the fuel cap. If there are fumes at the cap, they are likely getting through the bottom edge of the windscreen. I need to remove that strip and re-seal the windscreen.

A couple months ago, I over-filled the tank and gas spilled all over the top of the cowling right in front of the windscreen. There was strong gas odor in the cockpit for days. I suspected gas seeped down the outside of the filler neck and onto the top of the tank and inside the cockpit. Fuel also probably seeped under the strip at the bottom of the windscreen.

At this point, I'd like to remove the cowling around the tank to inspect the filler neck and look for ways to prevent gas from seeping into the cockpit if I over-fill the tank again (yes, I will try to be more attentive when fueling, but it's dark in there and hard to see the fuel level).

I also want to re-seal the outside edge (perimeter) of the firewall where it meets the cowling and all the holes to make sure none of the engine compartment air is entering the cockpit.

The sealant my mechanic recommended is a roll of grey, gummy sealant that looks like RV window sealant. I see there is also 3M Strip-Caulk. Any recommendations?

Do you guys have any suggestions that will make the job easier or the repair permanent?

Thanks,
Jim
Ashland, OR