Tip: Ethanol Compatible O-Rings

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!

Fuel cap

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

Cables inside fuel tank

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

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.)

Ethanol, Proseal and Fuel Tank Caps

Kyle Boatright said:

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

Click to expand...

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!

Excellent info!

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.

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

Standard ful caps

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

fuel pump

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

Bevan

newimaging said:

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

Click to expand...

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

Kyle, PRC DeSoto's PR-1440 (which is identical to Flamemaster's CS3204) is perfectly happy with ethanol. Check out page 2 of this data sheet:

http://www.bergdahl.com/PDF_Files/bapr1440b.pdf

"Resistance to other fluids - Excellent resistance to water, alcohols, petroleum-base and synthetic lubricating oils, and petroleum-base hydraulic fluids.

Chuck, that brown o-ring you have on the standard cap is most likely Viton. The ethanol-intolerant Buna o-rings are usually black. Viton can be brown, black (really a dark grey) or many other colors. What were your vapor lock symptoms? Under what conditions did it occur?

Finally Dan, on the Newton box there is a sticker with the part number "A 30 L-VNS". I'm guessing the "VNS" means it's a custom cap made for Vans aircraft. Makes sense, the flange seems to be machined to fit the fuel tank skin perfectly. Thanks for the advice on the fuel lube. I did use it quite sparingly, and my fuel tank tested out completely airtight, with no tape or anything else over the cap. Guess those o-rings are sealing well.

Lycoming Fuel Pump diaghram?

Bevan,
I hope you have more luck than I had in finding
the diaphram that you are looking for.
It is the one part missing in the ethanol compatible fuel system.
All other rubber parts can be found and replaced.
I know FrankH and others have solved the problem by using 2 electric fuel pumps but for those of us who want one mechanically driven fuel pump
the ethanol tolerant diaphram is one part that does not yet exist.
There is a market for this part.... Anyone out there knows how to procure such a part?

Fuel Pump Diaphragm

I won't claim to know a thing about fuel pump diaphragms, as I've never seen the insides of an accessory case mounted fuel pump, but for someone who REALLY wants to experiment McMaster sells Viton sheet in 1/8" and 1/16" thicknesses, A75 durometer. Is there a possibility that could be cut to fit? Or is the fuel pump diaphragm more complicated than that?

Vapor Lock

krw5927 said:

What were your vapor lock symptoms? Under what conditions did it occur?

Click to expand...

In a nutshell, symptoms were that the engine stopped running, completely. Conditions were using autogas in a hot engine on a hot day.

More detailed information is on my website. Scroll down to the "Auto Gas Section"

http://www.fdatasystems.com/chuck/flight.html

This also has very useful information:

http://en.wikipedia.org/wiki/Vapor_lock

What about fuel pump?

Chuck, vey interesting story.
What about your fuel pump gasket? Did it ever start leaking or did you use another fuel pump?
I wish someone could enlighten us on the inner workings of a Lycoming fuel pump and the possibilty of cutting a ethanol tolerant diaphram.

Manufacturer's Responses

Here are three-year-old e-mail responses from Tempest and Flamemaster when I queried them about ethanol effects.

The spec for sealant has not changed, so the response remains valid.

I remember reading somewhere (AvWeb?) not too long ago that one of the pump manufacturers was looking at supplying an ethanol-resistant aircraft pump. But for now, there isn't one. Perhaps there's an auto pump that fits a Lycoming. If someone was to discover and publish their findings, we'd all be grateful. I lack the motivation because there's a Phillips station a 1/2 mile from me that as corporate policy does not blend in ethanol.

Regarding making your own diaphragm, good luck. There's a lot more to materials science than getting out the pinking shears. I think a better option would be ditching the mechanical pump and installing dual electric pumps that are known to be resistant.

John Siebold
Boise, ID

From: "Vince Bechtel"
Date: Thu Jul 17, 2008 9:45:09 AM US/Mountain
To: "'John Siebold'"
Subject: RE: Fuel Pumps

Hi John,

I appreciate the reminder, but unfortunately after checking with one of our
engineers the type of buna rubber that we are using is not ethanol proof. I
was told that we looked at making our fuel pumps ethanol proof, but once we
matched up the cost and with the amount of fuel pumps sold each year we
would lose money as a company. The shelf life was also an issue, because of
the amount of material that was mandatory to purchase.

I know this is not the news you were looking for, but I did some further
research and found out that Brazil is using ethanol and replacing pumps
every 3 to 4 hundred hours. As far as an automotive fuel pumps are concerned
all of the new ones are ethanol proof.

If you have any further questions don't hesitate to ask.


Sincerely,

Vince Bechtel
Technical Sales Representative
Tempest Plus Marketing Group

-----Original Message-----
From: John Siebold
Sent: Tuesday, July 15, 2008 1:52 PM
Subject: Fuel Pumps

Hi, Vince,

At Arlington you asked for this reminder e-mail. My question is: are
the soft materials in the low pressure AC/Lycoming pumps sold in the
USA ethanol-proof? Additionally, you are to ask your fuel pump techs
how the pumps are modified for your So. American customers, since that
market has fuel concerns. Then, do you know of automotive applications
that use the same or substitutable low pressure pump with is ethanol
proof?

I want to harden all fuel system components, the fuel pump being but
one, against ethanol contained in automobile fuel. Even though I avoid
ethanol-laced fuel, we're getting more and more exposure to ethanol in
the USA, and ultimately may need to live with the miserable stuff in
aircraft as long as our foolish congress is in session. A positive
answer would be most welcome in the amateur-built experimental aircraft
community. There's a lot of buzz about this topic, and Tempest
trumpeting an ethanol-proof Lycoming pump (both high and low pressure
versions) would certainly help your sales.

___________________
Hello Doug,

The following response was sent to another customer with the same inquiry.
Basically it states that we do not test using that fuel, but as you read
further others have tested it and it doesn't appear to be a problem.

Linda

The following is Flamemasters response to the use of various fuels and the
CS 3204.

Flamemaster CS-3204 all classes, is listed by Cessna specification
CMNP021 and AMS-S-8802 as qualified for use in fuel tanks (reciprocating
and Turbine fuels) and pressure cabin usage

All Flamemaster sealants including CS-3204 are tested using JRF
(Jet Reference Fluid) as a reference medium. The particular JRF type is
chosen by the custodian of the specification and may differ between
custodians.

Actual fuels including Aviation Gas, Motor Gas with or without Alcohol,
and various Jet Fuels JP4, Jet-A are not used for either qualification
or acceptance testing of specific sealant compositions.

So, what they are saying is we have not and do not test with that type of
fuel. However, I have looked up data from another source. Published in
the Chemical Resistance Guide for Elastomers written and researched by Kenneth
M. Pruett in 1988 polysulfide was tested and found to be acceptable.

The book states as follows:

Alcohols, General (attack on polysulfide)

Less than 15% swelling in 30 days to 1 year and less than 15% in 30 days
to 1 year loss of tensile strength. Description of attack - AB - excellent,
little or no swelling or softening or surface deterioration.

Hope this helps.

Linda

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 ?



The calibration of the capacitive fuel guages is significantly different when alcohol is added to the fuel.

You will think you have alot more fuel than you actually have.

Mogas / Ethanol

In case it helps anyone,our parts are all auto industry parts and are all ethanol tolerant. This would include our Boost Pump for mechanically injected engines:
http://www.flyefii.com/add_components/BPM/BPM.htm
As well as our electronic fuel injection systems:
http://www.flyefii.com/EFII_desc.htm

Robert Paisley

Fuel Pump Gasket

N427EF said:

What about your fuel pump gasket? Did it ever start leaking or did you use another fuel pump?

Click to expand...

I am using a stock Lycoming pump that is not resistant to Ethanol. Since 100% 100LL is used for takeoff, landing, and ground storage the pump is only exposed to ethanol during cruise flight.

Doing a rough calculation, during the 800+ hours since using ethanol laced car gas, the pump has been exposed for 500 to 600 hours ~= 20 to 30 days of exposure.

EFII Pump FWF?

Let's say we would give up the search for ethanol compatible
rubber parts on a $250.- Tempest Lycoming fuel pump and instead
retrofit an existing fuel injection system.
Naturally it will already have one electric boost pump and necessary filters
and simply need a replacement for the engine driven pump.
To accomplish this, you would want to install it FWF to minimize plumbing.
Could your pump be installed forward of the firewall as a replacement for the
engine driven pump?
On a brand new installation I suppose it would be easier to place these pumps in the wing root or elsewhere behind the firewall.
Specifically I would like to know if your pump can tolerate the heat forward of the firewall?

"Could your pump be installed forward of the firewall as a replacement for the
engine driven pump?
On a brand new installation I suppose it would be easier to place these pumps in the wing root or elsewhere behind the firewall.
Specifically I would like to know if your pump can tolerate the heat forward of the firewall? "

We frequently have the pumps mounted firewall forward on EFI installations.
We just make sure that radiant heat from the exhaust is blocked. The 'kick plate" included with the pump assembly is the heat shield when used on the forward side of the firewall.

There is another possibility here. If one were to use our dual electric pump assembly and no engine driven pump, this would give a redundant electric fuel pump source. The complication is that you would then need a regulator downstream after the pumps and a fuel return back to the selected tank. This is probably a more complicated and costly solution than using the engine pump you mention.

Robert

This probably goes without saying, but to anyone contemplating going all electric with their fuel delivery system (myself included), please consider redundant power supplies for those pumps. Some folks feel comfortable with a small extra battery noting that their fuel pump consumes very little power and could run for hours on a small battery. Some folks want the security of a backup alternator. Whatever your pleasure, just make sure that the loss of an alternator belt, a faulty field breaker, failed brushes, fried voltage regulator, etc. won't make the big fan up front stop spinning.

Worth persuing

This is exactly why I think it would be worth to pursue an ethanol tolerant
mechanical fuel pump.
The good news is that a solution is at hand using 2 electric fuel pumps,
but those pumps come at a price.
Reading the response to RV7ator from Tempest it looks like the price of tooling up and the purchase of large quantities of material are the only hold up to the ethanol solution.
The Tempest Fuel pump sells for about $250 dollar.
Even if they had to charge an (outragous premium) of say $100.- dollar more
it would still be a bargain, both in price and simplicity of installation.
The price of 2 electric fuel pumps is not the only consideration
but also the added complexity to the electrical system.
A mechanical fuel pump simply bolts on in one place no questions about it.

I'm on the same quest as many of you, that is to safely use E10 in my plane. In my case I have a Glastar with a 150hp Lycoming O320-E2D. So far in this thread I haven't seen anyone mention carburators. Are there materials in the carb susceptible to the ethanol, and if so, replacement parts that are rated to handle the ethanol?

Any further info on the ethanol compatible replacement diaphragm for the Lycoming engine pump?

Thanks,

-Dj

Does any one know...

... if the stock Vans/Stewart Warner fuel sender gasket is ethanol compatible?

Thanks in advance,

Robin

RobinHou said:

... if the stock Vans/Stewart Warner fuel sender gasket is ethanol compatible?

Thanks in advance,

Robin

Click to expand...

Heck, I am not even sure it is AVGAS compatible!

I had them on my plane for about a month and they swelled and got kind of squishy - so I just pro-sealed the sender in place - no leaks (6 years)!

Paul