Tip: Ethanol Compatible O-Rings

[krw5927]

I really hope this thread doesn't devolve into yet another debate about the disastrous consequences of running ethanol mogas in a Lycoming. I know, I know, my plane will fall out of the sky. Been there, heard that.

In my endeavour to run mogas in my RV9, and realizing that ethanol-free mogas is getting harder and harder to find, I've decided that my fuel system needs to be ethanol compatible. I hope to be able to find ethanol compatible materials for every part of my fuel system as I build (note: no engine-driven fuel pump). So far the only parts of the fuel system I have are the tank drains and fuel caps.

Rather than attempting to contact the manufacturers and getting sometimes questionable data from them, I decided to just assume every seal and o-ring is NOT ethanol tolerant and set about carefully measuring for Viton replacements.

First, the fuel drains. These o-rings come in packs of 100. More than I'll ever need.






The Deluxe Locking Caps from Vans each have three o-rings:







The whole thing is rather simple to take apart and put back together, however I made sure to only disassemble one at a time in case I needed a reference for reassembly. I suppose I should probably use a little fuel lube on the new o-rings - any suggestions?

I have quite a few extras of each size, except the big cap o-rings, and I'm willing to share.

Hope this helps someone. Enjoy!

[frankh]

Mine has brown O rings which is normally indicates a Viton ring. In 500hrs (with a fair bit of neg G aerobatics) there has been no degradation.

I run mostly ethanol laced mogas.

Frank

[newimaging]

Kurt, I have capacitive fuel senders in mine, and am at the point where I have to solder the electric cable to it. If I want to build ethanol/alcohol safe, what do you know about the insulation on the cables, what kind of plastic is that ?
Also, would love a set of O-rings, if you PM me.

Christian

[Kyle Boatright]

A bit of thread drift, but how compatable is are B-2 sealants (proseal, flame master, etc) to ethanol?

That issue and questions about the mechanical fuel pump diaphram seem to be the chemical compatability issues still in play. (In the spirit of the original poster, not trying to broaden the discussion beyond the chemial issues.)

[chuckwn]

Originally Posted by Kyle Boatright

A bit of thread drift, but how compatable is are B-2 sealants (proseal, flame master, etc) to ethanol?

I think my response here is the thread drift that the poster was talking about, but here it is anyway:

Have been running Ethanol laced mogas for 6 years and 800+ hours in only the left tank.

No issues with proseal or Vans's standard fuel tank cap gaskets (brown O-Rings) so far.....
I did have to switch to a Viton sump drain as detailed by the poster. Be careful with vaporlock..... Learned this the hard way!

[N427EF]

Knowing the part numbers for all those o rings is very helpful.
Thanks for the legwork krw5927.

This post is even more relevant in the face of a recent lawsuit filed against
California retailers and producers of 100LL.
We'll be without 100LL before too long.

[guccidude1]

Any chance you could turn the deluxe cap box over so the Newton part number would be visible? I suggest using the fuel lube sparingly, too much will sluff off and fall to the bottom of the tank and be picked up during the fuel sample. Took me awhile to figure out where that sticky stuff was coming from after replacing and generously applying fuel lube to the Q-drain/cap o-rings every year. Thanks for the part numbers, Dan

[Bevan]

Does anyone have a part number for the two O-rings in the Vna's standard fuel caps?

[Bevan]

Does anyone have a part number for a viton (or ethanol compatible) diaphram for the typical lycoming fuel pump?

Bevan

[krw5927]

Originally Posted by newimaging

what do you know about the insulation on the cables, what kind of plastic is that?
Christian

Christian,

If the wire provided in the capacitive sender kit is standard aircraft wire (marked Mil-W-22759) then the insulation is Tefzel and I'm guessing it will be ethanol compatible. It sure seems to be resistant to MEK, which I would imagine is way more harsh to just about anything than ethanol would be. I tried to rub the green markings off the wire with MEK once and it wouldn't budge. Excellent stuff.

The wire isn't the big issue with capacitive senders though. From various anecdotal reports that I'm sure you can find on the forums, it appears that varying concentrations of ethanol can produce varying readings in the capacitive senders given the same fuel quantity. In other words, what your fuel gauge says is "full" on 100LL may not read anywhere near full with E10. This is the reason I went with float sensors. No matter what I put in the tank, 5 gallons will always read 5 gallons.

Kurt