Hey Guys....Looking for HELP. I have the same problem with my recently completed CH750 STOL as far as unequal fuel flow from the right and left tanks. SCARY!!! I flew about 40 minutes yesterday, starting with even tank levels of about 8.5 gallons in each, and landed with 4 gallons in the left and 8 gallons in the right. I have the vented caps that were supplied with my kit. Also noticed 100LL blue stain on my new vinyl covered right wing. A bummer. I plumbed both tanks straight across in the frame member above and behind the seats, with a "T" at the pilot side vertical door frame member and going down to the shutoff valve supplied, located at my left shoulder. From there I go to the gasolator, an inline filter and electric fuel boost pump located in the floor behind the pilot seat? Free flow from each tank is 1 gallon every 2.5 minutes, more than enough to feed my 0-320. If the left tank runs dry will I be sucking air, even if I have time to turn on the boost pump? I am waiting on an answer from Sebastian and Roger.

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Comment by Chris M. Brammer, Jr. on November 15, 2016 at 7:25am
Thanks for the input Guys. Will let you know if the snorkel vents make a difference and how things are going.
Comment by Bob Pustell on November 11, 2016 at 8:04pm

Certified planes that have both tanks plumbed together have the two tanks vented together also. This cross connection of the vents helps to minimize uneven flow due to uneven pressure inside the tanks. If I was building a 750 I would use a fuel tank selector and only run one tank at a time. That, to me, is less hassle than working up a cross connected vent system and it gives you the ability to not use a tank that has contaminated fuel in it or has sprung a leak.

Comment by Timothy D. McCall on November 7, 2016 at 12:44pm


My right tank always seems to have more fuel in it even though I set the valve to both AND return fuel to the pilot side tank only.  I have vent "snorkels" on top of the caps as well.



Comment by Phil Smith on November 6, 2016 at 10:57pm


Read with interest over the years about un-equal fuel flow.  I must have lucked out because I do not have this problem.  Why??? I never used the supplied tank caps but bought caps from Wag Aero.  For some reason I bought the E - 481 - 000 caps (call them and ask if the cheaper E - 476 - 000 caps will work).  I carefully bent the straight pipe at a little more than ninety degrees to face the wind - read constant ram air pressure on both tanks -  and my tanks stay level all day from start to a couple of gallons left. And because the vents are a couple of inches high they don't leak all over the top of the wing when the tank is filled up to the top of the standpipe.  As far as my plumbing: the two feeds are not of equal length  down to the Zenith supplied square aluminum gascolator on the bottom of the fuselage.  Try the new caps - might solve all your problems - just make sure that you have a seal at the tank to cap juncture - I keep mine lubed with white grease from time to time.


CH 701

Almost 200 hrs on plane 

Comment by John Austin on November 6, 2016 at 4:42pm

That's why I interconnected my tanks with an Andair fuel selector valve with "Left, Right, Both, and Off".  That way, you have independent lines from each tank so you can use one tank or the other to burn off imbalances and then use the "both" setting to interconnect them when desired.  There also is the advantage should you ever get contaminated fuel in one tank, you can shut that tank off and just run on  the other tank.



Comment by Bruce crum on November 6, 2016 at 3:28pm
I have the same problem with my 750 stol I now have 70 hours on mine and the other guys are correct when the left tank gets lower it will start using more fuel out of the right tank. Bruce.
Comment by Harmen van der Velden on November 5, 2016 at 7:01pm

very common observation ..In a lot of planes that have a both on the fuel selector... lentgh of fuel line left and right not the same a possibility , elbows and curves in fuel line etc,  wings level ??  However don't be worried because the flow will keep going even when the tanks are not even, meaning if the left tank gets low enough more fuel will come from the right, cessna (and 701) drivers are totally used to this

no worries,  Harmen

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