Zenith Aircraft Builders and Flyers
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701 Fuel tanks -- uneven consumption
Hello,
My 701, which I did not build, does not consume fuel from the wing tanks evenly. On a recent cross country, I consumed 5 1/2 gallons from the left tank and ~1 1/2 from the right. Obviously, this concerns me. I do not see any kinks in the line or anything obviously wrong.
Has anyone experienced this. Fixed it? I did not build the plane, but know that the lines from the 2 tanks converge in a sump. The line from the sump goes long the cabin floor on the left side.
Also, I have the constant smell of fuel in the cabin. I have read that this is not uncommon. Some have said that fuel will seep through the rubber hose enough to cause the smell. I do store it in a closed hangar which supposedly increases the smell.
My 701, which I did not build, does not consume fuel from the wing tanks evenly. On a recent cross country, I consumed 5 1/2 gallons from the left tank and ~1 1/2 from the right. Obviously, this concerns me. I do not see any kinks in the line or anything obviously wrong.
Has anyone experienced this. Fixed it? I did not build the plane, but know that the lines from the 2 tanks converge in a sump. The line from the sump goes long the cabin floor on the left side.
Also, I have the constant smell of fuel in the cabin. I have read that this is not uncommon. Some have said that fuel will seep through the rubber hose enough to cause the smell. I do store it in a closed hangar which supposedly increases the smell.
Replies to This Discussion
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Permalink Reply by Ernest Jessee on
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thanks. I will check this weekend. Oddly, the fuel cap on the right wing, the one that drains slower, spills fuel down the wing -- apparently at climb-out. I would have expected that to mean that the cap on the right wing is not sealing as well and thus would have expected the right wing to drain faster.
thanks again.
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Permalink Reply by Ben Haas on
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My 801 does the EXACT same thing. Right down to the right wing did spill fuel and the left one didn't. I switched the fuel caps and nothing changed. Since I did a custom dual tank install I added additional tank venting that exits below the wing, I epoxied up the vent holes in the stock zenith caps and that stopped the spilling. Altho it happened on my very first flight and that one event stained my Dupont Imron paint... So much for aircraft paint holding up to 100LL blue dye.. Don't get me started.... As for the uneven fuel. It has been thought over a lot. Common deduction is the prop wash spirals around the fuselage, hitting the bottom of the left wing and the top of the right wing. That uneven airflow " might" contribute to the quirk.
Other then that I LOVE my 801. !!!!!
Ben.
N801BH.
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Permalink Reply by Bob McDonald on
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Ernest
Check that both the fuel tanks are properly vented. Consider replacing the fuel tank cap on the fuel tank that does not appear to be delivering fuel with a new "vented" cap. If the tanks have vent lines.. "over flows" that exit under the wing, run stainless safety wire up the vent / drain until your positive it enters the fuel tank un-obstructed. Spiders & Mud Dauber Wasps tend to make nests in those holes plugging them. Fuel smell in the cockpit... replace the rubber lines with new premium quality fuel injection rubber lines. Rubber fuel lines should be replaced on a 5 yr frequency unless in direct sunlight. Use quality automotive fuel line clamps, not the stainless gear clamp style.. they tend to cut the line when over tightened.
Bob
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Permalink Reply by Rolf Grandstaff on
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Hey Ernest, fyi, there was an earlier discussion thread on the forum related to your problem out on...
http://www.zenith.aero/forum/topics/gravity-feed-from-wing-tanks
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Fantastic. Thanks.
Hey. I recognize your plane. It is at KNJX with mine now.
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Yeah man, birds of a feather...
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Ernest, I meant to ask you, when you do your power off landing at 60 mph, what configuration do you use for flaps and trim, if any? Thanks.
Hope you have a great flight up to Franklin county!
-Rolf
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Rolf,
I prefer no flaps. I have landed with flaps and no throttle, but it seems like the elevator is a bit less responsive at touchdown and the angle of descent can become absurd. Bouncing is more likely also as lift is increased.
So.. no flap and I set trim to neutral before I begin descent.
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OK thanks, Ernest. Appreciate the info. Yeah, flaps on this airplane makes it drop like a stone.
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Permalink Reply by Tommy Walker on
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Earnest,
I've noticed the same thing, only in my case, the fuel burns faster from the right tank than the left!
Some builders have added a positive vent tube to the caps to help pressurize the tanks. The tube is periscope shaped and faces the oncoming air.
Do you have these type caps?
The procedure for creating the vent tubes can be found on the Matronics Zenith List. Basically, you drill a hole in the cap and solder/weld the tube in place. You also have to solder/weld the two vent points inside the cap. Take a look at some of the pictures of 701's on the Zenith website and you will see an example.
If you need more info, email me at twalker(at)cableone.net
Tommy
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Permalink Reply by Chumphol Sirinavin on
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Earnest,
Apart from uneven fuel consumption in wing tanks that many have made comments, fuel fume, if not from known spill or overflow, needs a thorough installation check, with wing skin opening.
Good fuel hose does not allow fuel to seep through. Good fuel hose with good retaining strap and good installation has no fuel leak. Cracks on hose end, due to rough cut, bad installation, or over age, allow fuel to leak. A friend of mine uses aluminum fuel line inside wings so he does not need to replace the hidden rubber hoses every 5 years.
A 701 built in 1996 that I bought has very simple fuel system. 4 small wing tank, 2 in each, have common low connection point before engine. The 4 tanks uses flush vent fuel caps (available at Wicks Aircraft), with no fuel selector, no tank strainer, no tank drain. Fresh fuel trace under wing forced me to open the wings and found bad connections. One wing had an old rubber hose, probably left unchanged and cracking up on one end. Another had a plastic zip lock in place of steel retainer strap. I have not made long enough flight to note any uneven consumption. Float type indicator have not shown much difference between wings. I am glad I have found bad connections. If there is any other problem, I have to find out on next flight later this year.
Champ
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Permalink Reply by Robert Stacey on
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This seems to be a common problem with high wing aircraft. To avoid this, I was planning on running my lines to a 4 way valve with RIGHT, BOTH, LEFT and OFF positions.
Normal operation would be on BOTH. If fuel consumption was uneven ,switching to the fuller tank would aleviate this problem. Besides giving me control of which tank to use, this arrangement would prevent air from being sucked into the system if one tank did go dry.
As I am still a year away from finishing my 701 this is only my opinion.
Bob in Newfoundland.
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