Uneven fuel flow / overflow

tshort · Post by **tshort** » Sun Nov 25, 2007 2:20 am

I filled the 170 last night and flew back home, about 30 minutes.
When I pulled it back into the hangar, I noticed fuel stains on the top of the right horizontal stabilizer. Looking closer, the top of the R wing was wet, and there was a puddle in the top of the R fuel cap. Fuel had been spilling (siphoning?) out of the R tank and out overboard.

Annual is coming up this week; where should we look for the cause? Are the gaskets on the fuel cap not sealing well enough?

I know it feeds well from each tank if R or L is selected, but if it is on Both, it almost seems like fuel moves from the L tank to the R and maybe overboard. The vent is working fine - if I blow gently into it, air is audible in both tanks.

Thoughts?

Thanks

Thomas

blueldr · Post by **blueldr** » Sun Nov 25, 2007 3:31 am

If the fuel cap gasket is sealng, perhaps the "moat" gaskets are shot or the screws are loose, or both.

Swap caps across the tanks for a quick check.

tshort · Post by **tshort** » Sun Nov 25, 2007 6:22 pm

So are the gigantic fuel caps intended to be airtight and seal the tank? I am not sure how the system works. On the RV the caps are airtight and the tank is vented via separate vents. Is this the case on the 170 as well (vent via the vent above the cabin?)
If they are intended to be airtight then we have some work to do on the caps as they are not air or water tight at all...

Thomas

blueldr · Post by **blueldr** » Mon Nov 26, 2007 4:24 am

I believe there is one "ancient" AD that requires one vented fuel cap be installed. These caps have a rubber check valve that allows air to enter the tank but preclude air or fuel from egressing through the fuel cap.
The alternate fuel cap is supposed to seal the filler opening.