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701 Fuel Caps leaking

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jpspencer(at)cableone.net
Guest

Posted: Sun Mar 02, 2008 4:15 pm Post subject: 701 Fuel Caps leaking

Those with flying 701's

 Have you had a problem with your fuel caps leaking  and if so what did you do for a fix? I have tried about a half dozen different  gaskets and no success. Believe now that the fuel may be getting between the cap  and the doubler inside it and then sucking out.

 Thanks Joe

   [quote][b]

n801bh(at)netzero.com
Guest

Posted: Sun Mar 02, 2008 6:08 pm Post subject: 701 Fuel Caps leaking

Joe. On my 801 the fuel caps leaked on the very first flight and stained my Dupont Imron 300 bucks a gallon aircraft paint. I was not a happy boy......... The 701/ 801 wings are a very high lift airfoil and thus has alot of low pressure on top of the wing. If my tanks are 3/4 or more full they would leak through the caps by way of the vent system built into them. Luckily I had made provisions to vent all of my tanks from below the wing where high pressure exists. All I did was to epoxy up the vent holes in the caps and my issue went away. The other simple way is to solder on some forward  facing vent tubes onto your caps so they will slightly pressurize your tanks and stop the caps from siphoning out the fuel. I am guessing your problem only happens at full tanks?? 

do not archive 

Ben Haas

N801BH

www.haaspowerair.com



-- "Joe Spencer" <jpspencer(at)cableone.net> wrote:

 Those with flying 701's

 Have you had a problem with your fuel caps leaking and if so what did you do for a fix? I have tried about a half dozen different gaskets and no success. Believe now that the fuel may be getting between the cap and the doubler inside it and then sucking out.

 Thanks Joe

 	  Quote: 	
		  



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   [quote][b]

stepinwolf

Joined: 21 Jan 2008
Posts: 133
Location: Canada

Posted: Sun Mar 02, 2008 7:11 pm Post subject: Re: 701 Fuel Caps leaking

On more then one occasion, I have seen photos of forward facing vent tubes that are part of the gas cap.  As the previous post ( Ben ) explains, it serves to increase the inner tank pressure, there by eliminating the fuel leakage or siphoning from the fuel cap.



Would I be correct in assuming that with this type of forward facing vents, there most certainly would be some water ingested into the fuel tanks, were the plane to fly through low level clouds, or some rain showers.



Bob the 701 scratch



do not archive

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jpspencer(at)cableone.net
Guest

Posted: Sun Mar 02, 2008 7:47 pm Post subject: 701 Fuel Caps leaking

Ben

 Thanks for the reply. I brazed on forward facing 3  inch high fuel vent tubes while building the plane. I don't believe that's the  problem...am thinking it's maybe more of a problem with the double walled fuel  caps supplied by Zenith in the kit...the fuel may be getting between the 2 parts  of the cap and then getting sucked out regardless of gasket integrity???You are  correct in that it only happens when near full.

 Thanks again

 Joe

   [quote][b]

JohnDRead(at)aol.com
Guest

Posted: Sun Mar 02, 2008 8:33 pm Post subject: 701 Fuel Caps leaking

I heard that Zenith will modify the fuel tank caps to add the vent tubes,  if you ask nicely.

  

 John  Read



Phone: 303-648-3261

Fax: 303-648-3262

Cell: 719-494-4567   

  In a message dated 3/2/2008 7:09:53 P.M. Mountain Standard Time,  n801bh(at)netzero.com writes:

  	  Quote: 	
		     

Joe. On my 801 the fuel caps leaked on the very first flight and stained my    Dupont Imron 300 bucks a gallon aircraft paint. I was not a happy boy........    The 701/ 801 wings are a very high lift airfoil and thus has alot of low    pressure on top of the wing. If my tanks are 3/4 or more full they would leak    through the caps by way of the vent system built into them. Luckily I had made    provisions to vent all of my tanks from below the wing where high pressure    exists. All I did was to epoxy up the vent holes in the caps and my issue went    away. The other simple way is to solder on some forward  facing vent    tubes onto your caps so they will slightly pressurize your tanks and stop the    caps from siphoning out the fuel. I am guessing your problem only happens    at full tanks??   

do not archive 

Ben    Haas

N801BH

www.haaspowerair.com



-- "Joe Spencer"    <jpspencer(at)cableone.net> wrote:

   Those with flying 701's

   Have you had a problem with your fuel caps    leaking and if so what did you do for a fix? I have tried about a half dozen    different gaskets and no success. Believe now that the fuel may be getting    between the cap and the doubler inside it and then sucking out.

   Thanks Joe

 	  Quote: 	
		  



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  [quote][b]

n801bh(at)netzero.com
Guest

Posted: Sun Mar 02, 2008 10:09 pm Post subject: 701 Fuel Caps leaking

I think you are correct in determining that the issue is the area where the double walls are.  

do not archive

Ben Haas

N801BH

www.haaspowerair.com



-- "Joe Spencer" <jpspencer(at)cableone.net> wrote:

 Ben

 Thanks for the reply. I brazed on forward facing 3 inch high fuel vent tubes while building the plane. I don't believe that's the problem...am thinking it's maybe more of a problem with the double walled fuel caps supplied by Zenith in the kit...the fuel may be getting between the 2 parts of the cap and then getting sucked out regardless of gasket integrity???You are correct in that it only happens when near full.

 Thanks again

 Joe

[quote]



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vgstol(at)bigpond.net.au
Guest

Posted: Mon Mar 03, 2008 12:45 am Post subject: 701 Fuel Caps leaking

That's exactly right  Joe.  Need to solder or epoxy those little holes inside the  cap.

  

 JG

  

 Do not  archive

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rroberts

Joined: 04 Sep 2006
Posts: 50
Location: Birmingham, AL USA

Posted: Mon Mar 03, 2008 3:35 am Post subject: Re: 701 Fuel Caps leaking

I'll take two of those modified caps if anyone knows where to get them.  ZAC just emailed me back saying they couldn't provide the part??

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Rick
www.n701rr.com
www.ricksplace.info

John Bolding

Joined: 23 May 2006
Posts: 281

Posted: Mon Mar 03, 2008 4:49 am Post subject: 701 Fuel Caps leaking

Hi Joe,  How's tricks in  Miss.??    seal up the cap halves with proseal , had to do that  on a Pacer once.    John

 [quote]   ---

vgstol(at)bigpond.net.au
Guest

Posted: Mon Mar 03, 2008 5:03 am Post subject: 701 Fuel Caps leaking

Of course that vent tube  brazed to the top of the cap needs to go through the inner portion of the  cap as well, then the original holes in that inner layer are  plugged.   

  

 Those caps with that  original venting system are only suitable for a filler neck  that's well above the fuel level, like in a car gas tank.  If the fuel  sloshes up against the cap, like it will do in a full aircraft tank, they  will leak.

  

 The new vent tube only  needs to be 1/8" bore, and three inches high is enough to prevent fuel sloshing  up and out.  Bent so it's facing forward pressurizes it very slightly and  prevents it from sucking fuel out.  Bend it so that the very front is a bit  down and then rain doesn't get in.  There's no airflow as such into  the tube, just enough to replace fuel volume used and release fuel vapour  pressure.

  

 JG

  

  

  

  

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