Fuel drain from Aux into Main on 680FL

[Huck-Mag]

When I fill the right Aux tank and park the 680FL with the switch on MAIN, the right Aux tank drains into the main until there is only about 10 gallons left.

If I leave the switch on AUX, then there is no drain.  If I leave the switch on OFF, then there is no drain.

I'm about to check the switch, then will have to move on to the valves which are a real pain.

Any thoughts or previous encounter of similar problem? 

No problems with filling and any draining from the left Aux tank into the main.

Thanks!

Brent

[ghancock]

I don't think that is where it goes unless someone has modified your airplane.  The aux tanks from what I've always understood goes to your engine directly.  They do not filter through your main tank.  If they did then you wouldn't need to have an aux switch on the panel at all (which would be awesome!!!).  I would imagine the gas is leaking somewhere else and evaporating.

Glenn

[JimC]

It could be leaking down and then back up, just like Twin Cessnas. There's no direct connection between the main (tip) and aux (wing) tanks, yet a bad valve will result in fuel going downhill from mains to the valves and back up to the aux tanks.