Cloudy Fuel - Please Help
 

Has anyone seen anything like this. Sumped my left tank today...fuel blue and clear. Sumped my right tank...fuel was blue and cloudy/milky. I drained four 2oz cups, each one clearer than the last. The fourth sample was blue and clear. The aircraft (RV-6A) has been indoors, in my unheated hangar in NE Ohio. The temperature was about 35degF when I took the samples, but the overnight temperature was about 25degF. I am not the builder...it was built by Bob Barrett, in Clear Lake MN, completed in 2009. The wings were quick-build. My guess is that it's either ice crystals in suspension, or a substance breaking down in my fuel tank. Any thoughts?

Water can look murky/bubbly. Did you let the sample sit? if you let it sit for a few minutes the water will settle to the bottom.

I don't know about your case but we need to be especially careful of water/ice in the fuel in the winter.

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NTSB Identification: CEN14LA120
14 CFR Part 91: General Aviation
Accident occurred Thursday, January 23, 2014 in Ashland, MO
Probable Cause Approval Date: 09/24/2014
Aircraft: CESSNA 414A, registration: N414CJ
Injuries: 3 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

The pilot reported that, during the descent to the destination airport, the airplane?s left engine experienced a partial loss of power and that he attempted to troubleshoot the issue. Unable to restore the engine power, he secured the left engine, feathered the propeller, and advised air traffic control of the situation. Shortly after, the right engine experienced a partial loss of power and eventually only produced idle power. Unable to reach the destination airport, the pilot conducted a forced landing to a field. A postaccident examination of the airplane revealed ice buildup in the fuel manifold valves, the fuel strainer bowls, and the fuel strainer screens. The left fuel strainer bowl contained a 1 3/8-inch thick piece of ice. Fuel samples from both of the airplane?s fuel tanks and from the fuel supplier at the airport used to the fuel the airplane earlier in the day were tested, and no water contamination was found; the source of the water contamination could not be determined. It is likely that the loss of engine power resulted from water contamination and subsequent ice buildup in the fuel system.

Thank you for your advice. I'm going to take another sample tomorrow. I will let it sit a while and see if it separates out.

Take two samples. Let one warm up and see what it does. 100LL has a certain capacity for water, so if the sample clears up on warming it maybe that the water has re-dissolved in the fuel. Think "ice beer" (remember that craze?). The alcohol in the beer was concentrated by freezing a portion of water out as ice crystals and then filtering them physically, Leaving a beer with higher alcohol concentration.

You might try using a coffee filter to strain a cold sample of the cloudy fuel and see what you get.

Alternatively, freeze the fuel even colder and see if crystals grow to visible size.

Ain't amateur chem lab fun?

Fuel
 

Better yet drain the fuel and put it in your snow blower and put fresh in your plane.It could have been the airport help not draining the filters or the bottom krud in the tank don't take a chance with bad fuel.
Bob

Well we finally had some cold weather last night. I took a couple 1oz fuel samples this morning and they were cloudy. I put the samples in a warm room, and looked for cloudy crystals to melt, and the water to separate out. Unfortunately, that didn't happen. Instead, the cloudy particles have remained cloudy and settled to the bottom of the samples.

Thinking it may be a plastic/petroleum based product breaking down in the tank, I called the Van's Builder Assistance line and talked to Scott. Scott was unaware of anyone having this issue. From our conversation, I've derived a list of petroleum based products in the tank to include the tank sealant, the fuel sensor float, and a white plastic grommet on the wing rib, all these items installed or applied at the Philippine factory. Items installed or applied by the builder are the inspection panel sealant, the brown rubber fuel cap O-ring, and the fuel drain O-ring.

My priorities now are to 1) determine what the cloudy substance is, 2) isolate the source, 3) replace the source, and 4) cleanse/purge the fuel system. My AMT will take the samples for analysis. Hopefully, that will help us narrow down the source. Any thoughts, considerations or advice would be appreciated.

I would drain the tank and then refill with new fuel and see if the new fuel becomes cloudy. This would tell you whether or not it is the tank, or something introduced in the fuel.

Build should not be the first suspect
 

If the other tank is clear I would drain the one in question via a strainer as suggested earlier. Don't think I would start with the build if the second tank is still clear days later. I would review my fuel stops though.

This is #2 Diesel just a little past cloudy :D Ever since the government changed to the ultra low sulfur fuel we have experienced serious problems with this new fuel. Back before they changed the chemistry the #2 would cloud around -15 F now we get complete filter blockage at 5 F. I hope that our LL or auto 91 does not do anything like this.