Fuel tank vents

[mstomlinson]

When I fill the right main tank to the neck on my 1997 MX7 180C, fuel will sometimes run out the vent under the wing. I don't know how much fuel is lost, but I sometimes think up to one-half gallon is lost. I am not as concerned about the loss of expensive fuel as I am abou the mess it makes. Has anyone experienced this irritation? If so, is there a fix or change of practice that will alleviate the problem?

[aussieaviator]

All of the Maules that I have owned have done what you describe. The simple fix is to only fill to about an inch below the bottom of the neck. The amount of fuel left out is nothing ( except if you flight plan to run bone dry )
Brian

[210TC]

M5 full to the brim, only comes out vent when in a turn on the ground.

[montana maule]

Maule has a vent check valve kit that up grades to the new style. It eliminated most of the problem in my M-5 and it prevents pumping fuel overboard if you start the aux pumps too soon.

[maules.com]

It is important to have the fuel selector valve on 'left' or 'right' when filling the tanks. If the fuel level in the tips on the new type single vent system is above the top of the main tanks, because of dihedral, the tip tank fuel will attempt to flow to the already full mains. It will come out of the main tank caps or the vents. Sometimes there is dirt in the vent seal, or the spring is weak. The vent can be dismantled and the spring stretched a tiny bit to get better sealing.

[Ernie]

My MX-7 does the same thing if filled too full. I've learned to leave the tanks down a little ( an inch or so below the bottom of the filler neck) and the problem is resolved. I also never use the "both" setting on the fuel selector right after a fill up, because fuel seems to migrate from one tank to the other until I've burned a few gallons from both tanks.

Ernie