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Nic(at)skyhi.flyer.co.uk
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 Posted: Mon Jul 17, 2006 1:16 pm Post subject: Fuel tank vent |
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Fuel is expensive and unfortunately my RH tank decides to empty itself via
the air vent / drain whenever it is either full or it gets hot.
Our guess is that the air vent tube doesn't reach the top of the tank, hence
the pressure builds up and vents the fuel (If you open the filler there is a
gush of released air pressure). The LH tank behaves itself.
I don't want to remove the tank as I am flying - If I drill a 16" vent in
the filler cap of this problematic QB tank, will the tank empty due to
venturi in-flight - or is this the best solution ?
Any remedies to save my fuel bill - much appreciated.
Rgds, Nic
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denis.walsh(at)comcast.ne
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| Posted: Mon Jul 17, 2006 1:41 pm Post subject: Fuel tank vent |
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One cause could be a loose connection (internal) of the vent line-to-
inboard rib. This will allow the expanding air to force fuel
overboard until the tank is more than half empty!
check the vent line for integrity. If needed, It can be tightened
by removing the inspection plate and use a mirror to guide your
wrench to tighten it up.
You would be surprised how many of those forget to get themselves
tightened back up after loosening for riveting the tanks.
Denis Walsh
On Jul 17, 2006, at 07:13 548330007, Nic wrote:
| Quote: |
Fuel is expensive and unfortunately my RH tank decides to empty
itself via
the air vent / drain whenever it is either full or it gets hot.
Our guess is that the air vent tube doesn't reach the top of the
tank, hence
the pressure builds up and vents the fuel (If you open the filler
there is a
gush of released air pressure). The LH tank behaves itself.
I don't want to remove the tank as I am flying - If I drill a 16"
vent in
the filler cap of this problematic QB tank, will the tank empty due to
venturi in-flight - or is this the best solution ?
Any remedies to save my fuel bill - much appreciated.
Rgds, Nic
|
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khorton01(at)rogers.com
Guest
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| Posted: Mon Jul 17, 2006 1:56 pm Post subject: Fuel tank vent |
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On 17 Jul 2006, at 17:13, Nic wrote:
| Quote: |
Fuel is expensive and unfortunately my RH tank decides to empty
itself via
the air vent / drain whenever it is either full or it gets hot.
Our guess is that the air vent tube doesn't reach the top of the
tank, hence
the pressure builds up and vents the fuel (If you open the filler
there is a
gush of released air pressure). The LH tank behaves itself.
I don't want to remove the tank as I am flying - If I drill a 16"
vent in
the filler cap of this problematic QB tank, will the tank empty due to
venturi in-flight - or is this the best solution ?
Any remedies to save my fuel bill - much appreciated.
|
I would expect that you should be able to see the outboard end of the
vent through the filler cap with a mirror and a flashlight. Compare
the ones on the left and the right to see if there is a difference.
If the right one isn't up against the top of the tank, it could
explain the problem. I don't see an easy way to fix that. I think
the tank would have to come off, and you would cut a hole in the rear
baffle to provide access, then proseal a cover on.
If the outboard end of the vent line looks normal, another
possibility would be if the vent line inside the tank wasn't
connected to the fitting on the inboard rib. If this is the problem,
you could get at it via the access cover on the inboard rib.
Good luck,
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://www.kilohotel.com/rv8
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dan(at)rvproject.com
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| Posted: Mon Jul 17, 2006 2:25 pm Post subject: Fuel tank vent |
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| Quote: | If the right one isn't up against the top of the tank, it could explain
the problem. I don't see an easy way to fix that. I think
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Reach in (with some tool contraption) and bend it upward? The tubing is
pretty soft.
do not archive
)_( Dan
RV-7 N714D
http://www.rvproject.com
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Doug Gray
Joined: 10 Jan 2006
Posts: 112
Location: Sydney, Australia
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| Posted: Mon Jul 17, 2006 3:18 pm Post subject: Fuel tank vent |
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Nic,
The open end of the vent tube should be held in place with a small al
tab sharing with one of the rivets holding the filler neck to the tank
skin. As Kevin says you can see it with a mirror and light.
It is possible that the vent has become unhooked from this tab. A
little root canal work through the filler neck may be all that is
necessary.
Doug Gray
do not archive
On Mon, 2006-07-17 at 22:13 +0100, Nic wrote:
| Quote: |
Fuel is expensive and unfortunately my RH tank decides to empty itself via
the air vent / drain whenever it is either full or it gets hot.
Our guess is that the air vent tube doesn't reach the top of the tank, hence
the pressure builds up and vents the fuel (If you open the filler there is a
gush of released air pressure). The LH tank behaves itself.
I don't want to remove the tank as I am flying - If I drill a 16" vent in
the filler cap of this problematic QB tank, will the tank empty due to
venturi in-flight - or is this the best solution ?
Any remedies to save my fuel bill - much appreciated.
Rgds, Nic
|
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Gary.A.Sobek
Joined: 09 Jan 2006
Posts: 217
Location: SoCAL USA
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| Posted: Mon Jul 17, 2006 4:24 pm Post subject: Fuel tank vent |
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Nic:
Everyone else have told possible causes and potental fixes.
Just a warning. DO NOT dirll a hole in your filler cap. You will lose more
fuel when you are flying from the low pressure suction over the wing.
About all I can add to what others have said, only fill the tank part way to
see if it vents fuel on the ground. How low does it need to be before it
stops venting? If I fill my tanks, I will vent out some fuel in the hot sun
but it stops when the fuel quits expanding. Have you measured the amout of
fuel that comes out of the vent? If you get one or two liters and it stops,
it may only be expansion of fuel in a full tank. If you get more than 6 or
8 liters, then more than likely the vent line is lose at the bulkhead
fitting.
After the inspection of the vent line at the fuel cap as others suggested,
if it looks good, find a helper and a hose. Connect the hose to the vent
and blow into the tank. Have your friend look in the tank through the
filler to see where the air is coming out. Should narrow down where the
leak is.
Gary A. Sobek
"My Sanity" RV-6 N157GS O-320 Hartzell,
1,894 + Flying Hours So. CA, USA
http://SoCAL_WVAF.rvproject.com
----Original Message Follows----
Reply-To: rv-list(at)matronics.com
Fuel is expensive and unfortunately my RH tank decides to empty itself via
the air vent / drain whenever it is either full or it gets hot.
Our guess is that the air vent tube doesn't reach the top of the tank, hence
the pressure builds up and vents the fuel (If you open the filler there is a
gush of released air pressure). The LH tank behaves itself.
I don't want to remove the tank as I am flying - If I drill a 16" vent in
the filler cap of this problematic QB tank, will the tank empty due to
venturi in-flight - or is this the best solution ?
Any remedies to save my fuel bill - much appreciated.
Rgds, Nic
| | - The Matronics RV-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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hollandm(at)pacbell.net
Guest
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| Posted: Mon Jul 17, 2006 7:12 pm Post subject: Fuel tank vent |
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I vote for a loose connection at the bulkhead fitting, That would explain the ½ tank effect.
Note that Vans SB to safety wire and tighten internal fittings on 7 and 9 tanks includes the very fitting mentioned.
Mike
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zilik
Joined: 19 Jul 2006
Posts: 2
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| Posted: Fri Jul 21, 2006 11:18 am Post subject: Re: Fuel tank vent |
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We had a local builder that forgot to tighten the B nut on the vent line inside the tank. The full tank caught the afternoon sun while sitting in the hanger and started to drip just like they all do when the tanks are full. This one did not stop, just a steady stream started coming out and flooding the hangar floor. I pulled the cap and stuck my finger over the vent but that did not stop it. Since the owner was not there we put a five gallon bucket under the drain and closed the hangar door. About 2 gallons of fuel drained out before it stopped. Removing the tank and tightening the B nut fixed the problem.
Gary
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