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Fuel Contamination

Tailwind/RVGuy

Active Member
Hello All,
At the airpark where I live we had a fuel continuation issue and I would like your thoughts about what type of contamination this is and where it came from. There were four airplanes affected all of which fueled at this tank. Two of us had more issues than the others but ALL had evidence of some foreign liquid in their tank.
Here is some background followed by what happened. Long but it is important information. Access following link for pics. Zoom in on the one with the filter screen and the one that shows the little brass bowl at the bottom of the accelerator pump-- scary.

https://photos.app.goo.gl/g9J2F9MjSi9qzK3L9

• Fuel is on an airpark with two approximately 1800-gallon tanks for avgas.
• Fuel is not sold to the public.
• One compartment has been used for years with no problems. The second compartment had been empty, and we needed more capacity, so we hired a fuel tank cleaning service and had the tank cleaned.
• The supply tank fuel pump system has multiple screens and filters with the final filter being a canister filter that is designed to stop water from being dispensed.
• Back in late August 2022 I fueled at the tank. After flying to another airport my airplane quit on taxi at a low idle RPM. Started right up and I blamed it on the fact that I recently had my carb overhauled and figured I set the RPM too low. I have a wooden prop and it does not have much inertia.
• The next time I flew I drained the sump as always and got a sizable amount (half of my sample cup) of some yellowish colored liquid. This liquid had kind of an oily sheen and would leave residue on the side of the sample cup. After I drained it once that day, I did not get anymore so figured the issue was over.
• From that time on I did not fuel at that tank anymore but continued to get some of that yellowish liquid in my sample cup from time to time. Not every time but on a consistent basis.
• My friend in his RV4 also had similar problems. We then departed on a approx. week long trip where we each burned approximately 100 gallons of avgas from stops on the trip. We continued to get some yellowish liquid in our samples when sumping the tanks. It was as if it "hid out" in crevices and corners and drained to the sumps at strange times. One time in particular, We sumped our tanks in the morning with clean samples and then flew an hour or so and sumped them again and got some yellow liquid.
• Both of our engines are carbureted Lycomings
• After we got back we dug deeper and did some ethanol testing on the liquid and determined that it in fact was ethanol or some other liquid that would mix with water. We also discovered that this yellow liquid would turn to a jelly like substance that would stick to the sides and bottom of the tank. It would look like pepper sized soft particles that would eventually collect together to form large drops of jelly like substance.
• The cartridge filter on the (fuel dispensing) pump had an extreme amount of corrosion on the steel end of the filter.
• I checked my inline race car filter and found that it was almost completely plugged with a jelly like substance. See the picture in the link.
• Long story short, we determined that if we let it dry, the "jelly" would crumble and turn to dust. We both emptied our complete tank systems and dried them out using airflow from a muffin fan with a little heat to warm the air. We removed the carb inlet screens on both carbs, and they were both clean - no debris in either one. We thought we had the problem solved as we got clean sump samples and have not used fuel from the contaminated tank.
Here is what happened next-- see pics attached.
• My engine began to have a problem starting and had always started on about the 2nd blade with a simple pump of the throttle. That didn't seem to be working plus my throttle cable seemed stiff.
• I blamed the hard starting on the cold weather here in Wisconsin plus I don't have a primer
• For the stiff throttle, I disconnected the cable from the carb and discovered that it WAS NOT the cable at all but rather the carb arm moved really stiff. I determined that the accelerator pump was almost seized in it's bore. Look at the picture and zoom in on the little brass bowl with the screen in it. The screen is almost completely plugged with some gel like material completely filling the outside of the screen. Note also the white colored gel like material on the top of the check valve. This prevented any gas from being drawn into the accelerator pump plus the pump would barely move in the bore.
• Upon further disassembly of the carb I discovered more yellowish liquid in the bowl (this is 4 months or so after the contamination) and corrosion on various parts of the carb body. Also a lot of particles of jelly like material. The inlet fitting filter was still clean.
So some questions:

• The yellowish liquid is definitely ethanol or some other liquid that is an emulsifier. Where did it come from? Our fuel supplier assures us that they do not sell ANY fuel that has ANY ethanol in it.
• What concentration of ethanol would cause the corrosion?
• The tank cleaning company claims they did not use any type of emulsifier but rather just pumped out any remain liquid, inspected the walls and then scooped out any left o over debris in the tank. Does that sound like a good way to clean the tank? Is that the industry standard?
• What causes this liquid to turn to jelly when it sits in any one spot for a length of time ( in the filter or bottom of the carb)?
• This stuff (ethanol/water mixture) makes it through multiple filters in the liquid form (including a supposed water stopping filter). before turning to jelly and collecting in various parts of the fuel system. How does it do that?
• Any ideas of what else this could be and how to clean it up and get it out of the system completely? It does seem that by drying the complete system that it does fix it but my recent discovery indicates that I literally have to take the carb apart and clean it. I wrongly assumed that after I had a clean main filter and a clean carb inlet filter that my carb bowl and internals were OK it appears that was not true based on my recent discovery outlined above.
• Have any of you experienced this? if so, how did you eliminate the contamination? Did you determine the source of the contamination?
• We are confident that it is coming from the fuel dispensing tank. We cannot figure out what it is or how it got into the tank, and how it passes through all the screens and filters. Ideas anyone??
Keith
 
Could be contamination in the transfer hoses. In today's times, I would not be surprised if intentional.
 
;Not a chemist but most industrial ethanol is clear and so is water. Clearly ethanol will mix with water, but from my understanding will not create a jelly like substance. Over time, stale gas will produce a substance we call varnish (have no idea what it really is). That is a dark yellow, but usually forms a surface coating, like varnish, and does not create a gel and it is not oilly and genrally gasoline alone cannot make it liquid again. This is what clogs up the jets on your lawnmower when it sits full of gas over the winter. This is more common in auto gas and avgas has additives to prevent most of it.

I can't really speculate what it is but highly doubt it is pure ethanol. We have had ethanol in our gas for a couple of decades and I am pretty sure that if mixing with water created a gel and clogged things we would know about it by now. In fact we still use methanol to absorb water and burn it to get water out of our fuel systems. We used to use it over ethanol because it is less corrosive, before fuel systems were designed to tolerate it. My best guess is that the cleaning crew lied and used some chemical or agent to clean the tank and didn't flush it out properly or neutralize it.
 
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Based on those articles sounds like you got a load of ethanol gas. Is this 100LL or mogas? I think you might have to completely drain the tank and replace all the filters. It could also be now that the airpark is using the 2nd tank the turnover time for the fuel is to long unless you are using 100LL.
 
Schmegma. It has to be Schmegma....

As a side note that you already discovered, and separate to the prime issue here, water separating filters should be religiously replaced. They rust, which makes sense considering the job they are doing.
 
The airpark only stores 100LL in the tanks. It continues to look like somehow ethanol was introduced into the tank plus water somehow also ended up in the tank. So weird that that stuff will flow through the filters and then end up turning to "jelly" even though it had not been exposed to air.
 
Are the tanks above ground? If so condensation and then the rusting of the steel tank every day just like the dew forming on the grass it’s happening in the above ground tank each day every day and over time it adds up to lots of nastiness in the tank. If the tank is steel and doesn’t have an access hatch large enough to enter I doubt it got an adequate cleaning. Oily residue could be some type of rust inhibitors the cleaning folks added once they saw the amount of rust that had accumulated over the period of none use of the tank.
 
The tanks are above ground and do have a large access hatch. I can certainly see how the condensation day after day could add the water to the tank.

Thanks all for your replies and ideas.
 
Way back in the day whenI was in college and working line service, the semi that filled up our fuel farm with 100LL had previously carried pump gas and had about 20 gallons sloshing around in the bottom of one bay or another that made its way into our system.

This was before ethanol, but it turns out it had enough density difference that it separated out and showed up as clear samples when we sumped our own system.

Not saying this is the same thing, just that you said your supplier states that they don't sell anything with ethanol in it. At least in our case, a mixup was introduced on the truck, so it does happen.

I would think that the most obvious answer is that you've got something in your fuel farm that might warrant opening it back up and having a look-see.
 
Fuel tank

My experience is with approved tanks built for aviation fuel 100LL.
There are several types of tanks.
- steel tank painted inside, internal inspection every 3 year.
- steel tank painted inside and the bottom and up to 1/3 of the height coated
with epoxy. Internal inspection every 6 year.
- stainless steel tank, internal inspection every 10 years.
The fuel pick up is either fixed or floating and it never picks fuel from the bottom of the tank. Typically 4-5" from the bottom of the tank.
A fuel tank has a ventilator pipe with an over / under pressure valve.
This is to prevent free ventilation and water condensation inside the tank.
If water is found in this type of tank, it is almost always rain that leaks in to
the tank via the service hatch on the top of the tank.
The fuel tank has a water separator and filter. Twice a year the full volume of fuel is pumped around back to the tank so that particles stops in the filter.
The fuel supplier is a certified company with trucks approved for aviation fuel only. There is a trained person that is responsible for the aviation fuel tanks.
Fuel contamination is almost unheard of.
One thing I know is that tanks coated inside or built with epoxy are sensitive
for ethanol and can dissolve the outer layer. Composite aircraft tanks are almost always made of vinylester resin that can handle up to E10.
Ethanol is corrosive, but only at very high temperatures.
I have run E5 (Mogas) in my plane for more than 10 years with no problems.

Good luck
 
Has anyone taken samples to a chemist? Seems like a logical step, if only to be able to narrow down where it came from. For example, if it's ethanol it would be less likely that it was the tank cleaning outfit. But it could have already been in there and they just did a lousy job cleaning it out.
 
Randall,
That was our first thought but was told by the supplier and others that the there was no longer an entity in the state (what ever that means) that tested fuel samples. We have not believed that and are in the process of taking some of our samples to an independent lab to determine just what you said.
 
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