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REPLACING FUEL FLOATS - Anyone?

Gyrodoug

Well Known Member
Folks,

I have bad fuel floats/senders and want to install new ones. This is NOT my wheelhouse...

Has anyone done so? I'm not inquiring so much about installing floats during a build, rather how to replace floats with new ones on an existing airframe.

Pics and simple explanations greatly appreciated!

Thanks!!!
 
Yep - did this on an RV-8 not long ago to fix a fuel leak (sender not properly sealed on install, the rubber gasket did last 20 years however before it started to leak). Not hard to do while keeping the wings on the airplane. Go from underneath, not the top. Don’t forget to drain the fuel before starting.

Be careful to put the 90 degree bend in the float attach wire (the 3/4” or so that goes into the hole on plastic arm).

Why the need to replace them?

Carl
 
Fuel tsnks

Not hard on my 6A

Replace screws with hex head screw and use an Allen wrench to tighten

Throw away gaskets and use pro seal instead

Mating surfaces should be scraped clean . I use razor blades, 12” long automotive gasket scrapers and wire brushes.

Clean with MEK prior to install
 
Yep - did this on an RV-8 not long ago to fix a fuel leak (sender not properly sealed on install, the rubber gasket did last 20 years however before it started to leak). Not hard to do while keeping the wings on the airplane. Go from underneath, not the top. Don’t forget to drain the fuel before starting.

Be careful to put the 90 degree bend in the float attach wire (the 3/4” or so that goes into the hole on plastic arm).

Why the need to replace them?

Carl

Floats are 30 years old and we recently, carefully installed new a new MGL fuel gauge. Super erratic readings, as in, empty when full.... etc.

Thanks for the response!
 
Not hard on my 6A

Replace screws with hex head screw and use an Allen wrench to tighten

Throw away gaskets and use pro seal instead

Mating surfaces should be scraped clean . I use razor blades, 12” long automotive gasket scrapers and wire brushes.

Clean with MEK prior to install



Where/How did you access the floats? Again, I'm not a builder...

THANKS for responding.
 
Floats

Where/How did you access the floats? Again, I'm not a builder...

THANKS for responding.

The floats are located at the fuselage end of the wing you must remove the long strip which is a trim between the side of the fuselage and the wing at the root once you remove that you’ll be able to see the round metal plate with a wire going to the center of it that device is the fuel sender float device if you’re in there there’s certainly no point in just replacing the float itself I doubt that the float itself is leaking or if it causing your erratic readings before I went through all this I would try to make sure that your floats are really bad or your sender is really bad it’s a lot of work but it’s nothing you can’t do, remove the wire remove the screws take the sender off clean as necessary you can replace it with a rubber gasket or a cork gasket if you wish. it has been suggested that you use pro seal. pro seal is definitely the the more permanent solution very difficult to replace later if you need to replace it later that would probably be doubtful at this point.
 
Do not use any gasket as history has shown others had issues with anything more that Proseal, but some not. It is not permanent using proseal, comes out with thin blade under an edge. NOTE: replacement OEM style senders come in a LEFT and RIGHT version….order the correct one for your need. (Vans). right or left wing.

https://store.vansaircraft.com/ie-f-385c-stewart-warner-right-tank-fuel-sender-ie-f-385c.html

https://store.vansaircraft.com/ie-f-385b-stewart-warner-left-tank-fuel-sender-ie-f-385b.html
 
Check your ground wire….

…if you have one!
Many early builds did not have a ground wire. It was assumed that the screws holding the sender into the tank would make the ground. I believe early plans didn’t show a ground wire?
Anyway, if you don’t have a good ground, you can get erratic readings as you describe.
Adding a ground wire isn’t hard. A ring terminal under one of the sender screws wired to a good aircraft ground or back to your grounding lug. Scuff up the area under the screw head. If you don’t drain the fuel, it will likely leak out of the screw hole so either drain the fuel or work fast. You will need a small amount of Proseal to “dip” your screw in to reseal the screw threads.
If you do need to replace the senders, I wrote up my experience with doing it many years ago. Perhaps a search will find it.
 
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Many early builds did not have a ground wire. It was assumed that the screws holding the sender into the tank would make the ground. I believe early plans didn’t show a ground wire?

They still don’t (except for the RV-12 plans)

Instead, they specify that an external toothed lock washer be used under one screw for the cover plate and one screw for the sander flange. This has worked well for ensuring a good ground path to the main part of the airframe.
 
Floats are 30 years old and we recently, carefully installed new a new MGL fuel gauge. Super erratic readings, as in, empty when full.... etc.

Thanks for the response!

So, things were normal until you put in the new fuel gauge and now *both* tanks read screwy? Is that correct?
 
In 22 years both my floats eventually sunk and had to be replaced. So it does happen! The new ones are improved I believe. In any case I had to do it and I found a good tip somewhere on VAF re. how to get the Prosealed access plates off: use a thin 1" or so wide putty knife, filed or ground to a sharp edge. Works like a charm. Once off use razor blade etc. as other posters mentioned to get it all off. And replacing it, I agree no gaskets, Proseal is really the only reasonably reliable way to do it without leaks.
PS. I did remove the tanks from the wing to do it. Kind of a bigger deal if the screws are painted over but mine are not. On the -6 it would be difficult to get the plates / senders off with the tank on, I'm not sure about the -8.
 
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