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Fuel pump overflow

wirejock

Well Known Member
Has anyone used AN hardware for the fuel pump overflow?
Vans suplies a 1/8" pipe to brass tube fitting and plastic tube. Lots of RVs flying with the Vans solution and I know there's no fuel there unless the diaphram fails.
I would like to use AN harware.
I would like to use a 822-4D fitting to aluminum tube.
90 degree 1/8" pipe to flare.
Is the aluminum aluminum fitting ok?
 
That is what I do, standard aluminum elbow and a piece of 1/4” aluminum tubing.

But - you must secure the other end of the tubing as it will fatigue and break off if you don’t. I use an adel clamp on the engine mount.

Carl.
 
Overflow

That is what I do, standard aluminum elbow and a piece of 1/4” aluminum tubing.

But - you must secure the other end of the tubing as it will fatigue and break off if you don’t. I use an adel clamp on the engine mount.

Carl.

Thanks sounds like a plan
 
That is what I do, standard aluminum elbow and a piece of 1/4” aluminum tubing.

But - you must secure the other end of the tubing as it will fatigue and break off if you don’t. I use an adel clamp on the engine mount.

Carl.

I'm surprised *that* method doesn't fatigue and break given the relative motion between the pump and engine mount.
 
Plastic tube

Another option.
Section of aluminum tube from the flare.
Clamp or safety wire rubber fuel line to absorb the vibration.
Just trying not to use a soldered brass tube fitting.
 
Another option.
Section of aluminum tube from the flare.
Clamp or safety wire rubber fuel line to absorb the vibration.
Just trying not to use a soldered brass tube fitting.
I would recommend some flexible tubing somewhere in the path to account for the "wet dog" movement at startup and shutdown. If that tube cracks, then you have an issue with the fuel pump, it will spray a nice mist of fuel on the hot exhaust, which could result in a bad day.
 
It's a pump tell-tale, clean and empty until the pump fails. The real goal is to make the failure obvious, so use clear poly tube or nylaflow. You want a tube which stains and appears overall black or blue given just a cursory glance, if/when it spits out oil or fuel.

It's real easy to miss fluid escaping from the end of an aluminum tube in the airstream, as there is usually very little of it. The weep hole in the pump has a tiny internal restrictor.
-
 

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It's a pump tell-tale, clean and empty until the pump fails. The real goal is to make the failure obvious, so use clear poly tube or nylaflow. You want a tube which stains and appears overall black or blue given just a cursory glance, if/when it spits out oil or fuel.

It's real easy to miss fluid escaping from the end of an aluminum tube in the airstream, as there is usually very little of it. The weep hole in the pump has a tiny internal restrictor.
-

Thanks for the pic Dan. That hole is smaller than I thought.
 
Another option...

After having to re-solder the original 1/8" NPT square plug + copper tubing version, I decided to find a better solution.

Parker W369PLP-4-2, + some 1/4" tubing (fridge water line, static system line, etc.)
 

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Has anyone used AN hardware for the fuel pump overflow?
Vans suplies a 1/8" pipe to brass tube fitting and plastic tube. Lots of RVs flying with the Vans solution and I know there's no fuel there unless the diaphram fails.
I would like to use AN harware.
I would like to use a 822-4D fitting to aluminum tube.
90 degree 1/8" pipe to flare.
Is the aluminum aluminum fitting ok?

my RV7 fuel injected has now 35 hours on it. i installed the fuel overflow with brass fitting and nylon tube but, honestly, never got familiar with the purpose of the device. from the beginning the transparent tube was blue from AVGAS and i thought it does what it is supposed to do.

could that be from high pressure when running the boost pump? or could there be a real problem?
 
good thread

my RV7 fuel injected has now 35 hours on it. i installed the fuel overflow with brass fitting and nylon tube but, honestly, never got familiar with the purpose of the device. from the beginning the transparent tube was blue from AVGAS and i thought it does what it is supposed to do.

could that be from high pressure when running the boost pump? or could there be a real problem?
Kay, you are going to love this thread.

https://vansairforce.net/community/showthread.php?t=160388

But probably not what it means for your wallet. :(
 
Fitting options

Ok. Back to the drawing board. I'm begining to see why Vans designed it the way they did.
The slip fittings have a max temp very close to the temp in the cowl. Maybe not a good idea. AN fitting doesn't allow for a clear tube to see fuel stain. Time to visit the Aviation isle at Ace and look for brass options.
1/8" pipe 90 to clear tubing type refrigerator water connection?
1/8" pipe 90 to barb?
 
Ok. Back to the drawing board. I'm begining to see why Vans designed it the way they did.
The slip fittings have a max temp very close to the temp in the cowl. Maybe not a good idea. AN fitting doesn't allow for a clear tube to see fuel stain. Time to visit the Aviation isle at Ace and look for brass options.
1/8" pipe 90 to clear tubing type refrigerator water connection?
1/8" pipe 90 to barb?

If you're worried about temperature exceedances, look at the Parker W169PLP-4-2. It's rated to 200°F.

Generally speaking, nylon tubing is rated to 200°F, PE to 150°F, Tygon to 165°F, and so on...

Failing that, you can always use a brass elbow/compression fitting affair with the brass insert & compression ferrule for 1/4" nylon tubing (sort of like the brake lines setup Van's recommended in DWG 36.)
 

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...and an image from the RV-14 plans...
 

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Generally speaking, nylon tubing is rated to 200°F, PE to 150°F, Tygon to 165°F, and so on...

True, BUT, that's for a pressurized application. The overflow hose isn't pressurized. Given that the melt point of nylon is typically over 300F, there is no real concern using it in this application.
 
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