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Permalink Reply by Tommy Walker on April 8, 2009 at 8:11pm

Raymond,

We had the same problem. Maybe not twice as much, but the left tank always took more fuel when we refueled.

If you are familiar with the Matronics list, Http://forums.matronics.com you might want to search in the Zenith and 701/801 lists for answers.

We put the perisope type pressure vent tubes in our wing tanks and that helped a bit.

I'm not sure, but it seems the distance from the left tank to the gascolator is a bit less than from the right tank.

But, our Cessna 175 did the same thing.

I wonder if people in the Southern Hemisphere have the opposite problem?

Interesting.

Regards,

Tommy Walker in Alabama

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Permalink Reply by Robert R. Kissell on April 9, 2009 at 4:18pm

Check the matronics site. I recently wrote and posted test results that might help with this. I also had the same behavior which I solved by the addition of snorkel vents to my fuel caps. I also ran a flight experiment where I created an empty tank to see what would happen. This and more can be found on the other site.
regards,
Bob Kissell N701UB 100+ hours

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Permalink Reply by Raymond A. Miller on April 9, 2009 at 6:05pm

Thanks for your research and the others that responded. You have eased my concern and I will work on those goosneck fuel caps. Too bad that they are not available commercially at least I have not been able to locate any. Cheers, Ray

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Permalink Reply by Chumphol Sirinavin on May 14, 2009 at 5:34pm

Ray,

You can drill a 1/8" or 3/32" hole on the fuel cap. Bend a length of metal brake tube to shape and braze it over the hole. Be careful when twist open or close the fuel cap, and not twist off the goose neck.

On a visit to Zenith Air, I took picture of the fuel cap atop the demo airplane. The vent tube was brazen to the fore-aft crest of the fuel cap. I can not find it now but will draw terrible pictures for you, from my vague memory.

Champ

Attachments:

• vent tube fuel cap.png, 302 KB

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Permalink Reply by Einar Arne Kleiven on September 28, 2009 at 1:14am

I like the idea to "pressurize" the gas tank, but what about the "enormus" low pressure above the wing!! Doesent that low pressure suck the tank, instead of pressurize?

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Permalink Reply by Chumphol Sirinavin on September 29, 2009 at 3:01am

Elnar,

You are right. Over wing area has lower pressure than under wing. But do not worry. There is enough pressure to keep fuel flowing. It has worked and it will keep on working.

Champ

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