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Fuel filter inspection tips

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On 5/6/2020 at 10:06 AM, Tip said:

I have seen that fuzz in the filter screens before. Your valve has probably been collecting it since new. I found the Mr. Funnel to be a pain. It doesn’t drain out completely and that little quantity of gas makes a mess.

The reason the Mr Funnel does not drain out completely is because the bottom section is actually a water sump and so is necessary for the correct function of the filter / water separator.  I am a big fan of the Mr Funnel and use it all the time even to fuel from a bowser or to transfer from fuel can to can. Each time you use it you should check the remaining fuel in the bottom foe water droplets, it is not just a filter but will also filter out suspended moisture.

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Prior to making a couple of changes in operating & maintaining my CTLS, I experienced a couple of partial power loss incidents. I’ve since found that corrosion products originating in the carb bowls can plug your jets.  Below is a link to the Kathryn’s Report covering the investigation into the 2016 fatal accident that occurred at Fond du Lac.  Read especially the section on the carburetor inspection.  This is an extreme case, but it’s an eyeopener.  I’ve found the same phenomenon in both carb bowls of my airplane, but to a much lesser extent. These days, I inspect & clean the bowls every 3 months and have begun limiting ethanol, and the engine never misses a beat.  At some point, I may replace the bowls since the “black areas” seem to breed this stuff, but the cleaning regimen isn’t a big deal.  

http://www.kathrynsreport.com/2016/07/flight-design-ctls-accident-occurred.html

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I've been burning rec gas 91 which is available at airport not far from home base, and with recent auto fuel prices as low as they are, recently considered buying 93 auto.  Filled a couple jugs last week at local station, tested and seeing perhaps 1-2% ethanol amount, have yet to pour in the CT.  This has me thinking I'll stick with the non-ethanol fuels.  With all of the oil capacity we have these days, I wish ethanol would be axed from entire supply channel.  I love farmers but can't stand what ethanol has done to harm things, boat motors, etc.

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When I first joined the forum and acquired the plane, I was an idiot on gas.  My position in the early days was to buy 100LL at the airport, thereby supporting the airport and bite the bullet on the oil changes.  An A&P pal told me that auto gas fumes in a hot hangar is a nightmare.  It isn't.  And several forum members told me that.

I went to "Rotax School" a year ago and learned that the 93 auto, e-10 gas available at nearby gas stations is "thumbs up" according to the Rotax pros.  And that is what I have been burning ever since.

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Between Swift 94 in Michigan & Indiana and non-ethanol auto gas, I’ve managed to avoid ethanol for a year and a half now, and it seems to help, at least in my case.  You don’t find many vintage car owners with nice things to say about what it does to carburetors.

 

 

 

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There was an interesting article a couple months back in EAA Sport Aviation.  An aircraft equipped one tank to be auto fuel and the other for avgas and would only burn the auto fuel in flight then switch back to avgas prior to landing.  This allows the resting phase of engine to contain the safe and stable 100LL, and limit the exposure and long term issues of the corrosive nature of the auto fuels.  

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Hi John, Phil and I are wondering when we'll see you here in Michigan?  Thanks for the link to the crash report.  I have taken my carb bowls off as required at yearly inspections and recently had the bowls removed for replacement of the carb floats.  The floats were defective and had absorbed fuel.  My carb bowls are not corroded as yours are.  Perhaps your CT sat and had water in the bowls before you bought the plane and this caused the bowls to corrode?  I'm thinking the bowls are aluminum and are anodized?  If water sets it might eat away the anodizing and then the corrosion cannot be stopped?  Or, if they're zinc, the water will corrode the zinc.  There is no doubt that alcohol free MoGas (low lead) fuel is best but 91 octane non-alcohol fuel is not nearby.  For my use of fuel, I have been using 93 octane "Premium" MoGas since 2009.  This has 10% or less alcohol.  My carbs have remained clean and have not needed balancing now for the last 5 years.  What I also do though, is add 2 oz. Marvel Mystery Oil to every 5 gallons of the MoGas.  My mechanic (Helicopter Dave) advised me Marvel Oil will stabilize the fuel and it allows any water that may be in the fuel to be absorbed into the fuel and then passed thru the carb and thru the engine.  Don't know if true but I've never found any water in the bowls or in the fuel when I sump and I have had no issues using MoGas all these years.  Good photos and discussion on our CT fuel system. 

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Hi Dick - I’ll probably return in early June, and am looking forward to some mid-west aviating.  My airplane was five years old with only 105 hours on the Hobbs when I bought it. So it spent several years sitting in a hangar in Texas, and I believe that’s probably why I’m having this problem when others are using ethanol fuel with no issues. However, I posted that info because like me, many probably assume that if the fuel is properly filtered & sumped, no debris or water can show up in your carb. Not so, at least in my case.  Funny thing is, I drain the sump before every flight, and never see water, but I do see it in the bowls from time to time. I had always assumed the bowls were aluminum, until I read the Kathryn’s Report on the accident. Surprise, I guess they’re cast zinc.  Now that I’m aware of the issue, it’s not a problem but I’ll probably replace the bowls at the next annual. Thanks for the info on MMO. 

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My plane was run exclusively on 100LL until I purchased and the bowls has some minor corrosion.  I have seen the carbs (912 and the 2 stroke 503 dual carb) completely covered in condensation after a quick short flight.  Likely the same on the inside.  With ethanol, this gets harmlessly absorbed.  Without it sits in the bottom and causes corrosion (100LL or ethanol free will both do this).  I have been running 93 MoGas (with ethanol) almost exclusively for 6+ years and have never seen this since then.  Pros and cons to both fuels but, most experts believe that long term, ethanol is better than lead.

 

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Agree with Matt.  I've burned MoGas since 2010 exclusively.  No corrosion in bowls and no balance needed on carbs for last 4 years.  As mentioned in previous post, I put 2 oz. Marvel Mystery Oil in 5 gallon cans.  Not sure if this has helped me stay trouble free but my mechanic who maintains all kinds of engines says it does help the fuel absorb any water that might be in the fuel.  I fly often enough that my fuel doesn't sit too long and keep my CT in a unheated hangar with engine heated.  These things make a difference on how much condensation is introduced into the carbs.

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Just helped a friend fix his CTLS that lost power after takeoff.  The carb bowls had corrosion in two of the corners where it did look like someone snubbed out a cigarette.  I popped off a 1/8" flake of tannish yellow "scab" from one of the corroded spots.  A main jet blocker for sure.  After clean-out, all is back to normal, until the corrosion flares up again.

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Flollow up.
After cleaning out the debris in the the fuel cutoff Valve I noticed something hanging down into the valve. I disassembled the valve and found teflon tape on the threads. A straggly piece of the tape was protruding into the the valve providing a slight obstruction upon which the debris could accumulate.

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Half way through the 16 hour class this weekend here, topic of bowls and corrosion came up, instructor suggests two things.  First, if plane is setting for more than a week, shut off fuel valve and let the carbs run dry.  Second, Bing has a carb bowl that is coated to prevent corrosion.  I'm not immediately jumping to either of these, I fly at least once a week, will consider that come winter time.  No info on the carb bowls, knowing how many corrosion issues have occurred in bowls that might be smart, will research them.

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I have been running 93 octane e10 fuel from the local BP station for about six years now.  I run 100LL when I have to when traveling, and have run a few other stations' 93/e10 fuel on occasion.  I have never had any fuel-related issues.  I had a tiny bit of corrosion in the carb bowl bottoms and gascolator bottom a couple years in, but they have not recurred and might have been related to the previous owner's fuel practice (he was old school and I suspect he ran exclusively 100LL).  I have never had more than a few stray grains of material in my fuel line filter, no flow issues, no junk in my fuel or carb bowls.  I drain a fuel sample before the first flight each flying day, and can count on one hand the number of times I have seems *anything* in the fuel, it's usually a super tiny fleck or two.

I suspect (but can't prove) that fuel contamination issues in CTs are cause by a few issues:

1) Possibly poor QA in FD production.  Some seem to get a lot of white/tan/translucent debris, this looks to me like it comes from the fuel tanks, possibly bits of composite or flakes of the fuel-resistant lining material.  This should have been cleaned out after the tanks were finished, but might have been left behind.  Luck of the draw on whether a particular airplane is affected.

2) Poor hose change procedures.  When doing the five year rubber change or any hose change, the new hose section should be cleanly cut with a quality tool that leaves no ragged edges behind.  It' also a good practice to blow new hoses out with compressed air to clear out any cut hose flakes, dust, or debris from manufacture.

3) Corrosion.  This is probably due to water suspended in the fuel.  Most mogas doesn't seem to have a serious issue with water, but over time even small amounts of water will corrode metals.  The corrosion usually takes place in the carb float bowls or the gascolator.  Corrosion doesn't happen overnight, so the solution is pretty simple:  inspect your carb bowls and gascolator bowl often, at least once a year during your condition inspection, more often if you can.

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