Fuel Vent Leak

[WitchesBoyToy]

M5 leaks fuel out of right wing from the forward of the two vents behind the strut. Noticed right tip and left main seem to be down a little gas. Fuel selector set to one of the main tanks, not both.

[Kirk]

Do you mean siphoning when the tank is filled or does it do this when not filled?

If you have aux tanks and 2 vents on each wing, you have the original old style vent. Forward 1/4” is main tank, aft 3/8” is aux tank. My most Maule savvy IA tells me changing to the newer single outlet vent (1 per wing) reduces the overflow siphoning.

I haven’t tried that. Still have the original as you do and added the check valves to the aux tank vent line which didn’t help much.

It does help siphoning if the vent line is curved upward where it exits the tank within the wing. There is not much space to do that but that slight rise above the tank vent outlet helps break the suction. Take care bending the line that you do not crack it when bending.

I carry a length of fuel line with me. 1 piece 3/8” ID and 1 piece 1/4” ID, joined together with a plastic 1/4” to 3/8” OD adapter fitting. Each hose is about 10” long. If any vent is siphoning after fueling, I fit the tubing over the vent while pinching the tubing closed, then blow through the tubing and release the pinched line. The vent line is purged back to the tank and usually breaks the suction. Keeping the line pinched until you start blowing is key. I’ve never gotten a mouthful of fuel that way and don’t ever want to.

Kirk

[montana maule]

You could also call Maule and get the mod kit to change to the new style vent and check valve set up. That will eliminate the problem.

[bobguhr]

X2 what Montana Maule said, I had Maule Flight install the new style vents/check valves on my M6 and the problem did go away.

[WitchesBoyToy]

You could also call Maule and get the mod kit to change to the new style vent and check valve set up. That will eliminate the problem.

Do they respond back now? Called them a couple weeks ago. No answer, just a message to send them an email, which included exactly what I wanted to buy, which they ignored. That's the third time in the last 6 months this has happened. Terribly unimpressed.

[asa]

You could also call Maule and get the mod kit to change to the new style vent and check valve set up. That will eliminate the problem.

Do they respond back now? Called them a couple weeks ago. No answer, just a message to send them an email, which included exactly what I wanted to buy, which they ignored. That's the third time in the last 6 months this has happened. Terribly unimpressed.

Just keep calling them. They’re great, but not by email.

[Andy Young]

My experience is that you have to keep calling until you get a human. Voicemail messages and emails are typically not returned. Oddly enough, I have had better luck just hanging up; sometimes I get a call back shortly thereafter when I do that.

Once you actually get someone on the phone, the service is typically excellent.

[whittakerw]

You could also call Maule and get the mod kit to change to the new style vent and check valve set up. That will eliminate the problem.

How labor intensive is this? Easy swap?

[DavZeeMXT]

I have the check valve setup in my M7. If a fuel person fills the tanks to the brim, fuel will flow from them so I always try to leave it down a bit.
Also if you fuel to full tanks and the plane sit in a warm place and the fuel expands, then it will leak from the vents. Sitting on an uneven surface has caused this too as I think the fuel will flow from one wing to the other and over fill it.

[netconn]

For those that don't know, when the fuel valve is in the OFF position the fuel is ported open between the left and right main tanks. If you want to stop the valve from being open between the mains you can set the lever in the middle of OFF and LEFT or OFF and RIGHT.

[Andy Young]

Or just set it to “Left” or “Right”. That won’t stop fuel from going to the engine of course, but it will stop it from flowing from one tank to the other.

[gbarrier]

If you want a true off switch to the Andair valve.