Rogerck Posted February 1, 2012 Report Share Posted February 1, 2012 My partner and I had the rubber replacement completed recently. The plane flew normally, power, rpm, indicators, etc. for the first couple of hours. On the third flight out, after a couple of landings in the pattern, I experienced a power loss on climbout from full throttle to 4000 rpm. I was able to land the plane safely on the runway without incident. The problem turned out to be debris from the hose change that accumulated in the float bowl, and was creating a blockage of some sort under full power. Thanks, Roger Lee, for conferring with my mechanic to quickly diagnoss and remedy the culprit. My mechanic was mindful of not getting debris in the fuel system during the hose change. Despite his precautions, it happened anyway. Here is his suggestion for future changes: After the hoses have been completed and with the carb bowls off, let each carb drain a couple of gallons of fuel (into a container) to clear the lines of any junk. I'm sure some are doing this already, but I wanted to pass this along anyway. Roger Kuhn Link to comment Share on other sites More sharing options...
Roger Lee Posted February 1, 2012 Report Share Posted February 1, 2012 This debris can happen even if you are careful. The hose gets pushed over the ends of the fittings and little pin head sized rubber flecks can get broken or shaved off. This is usually down stream of the filters so the next destination is the carb bowl. Under light throttle settings of 3500 or less, like during the carb balance, there usually isn't enough turbulent fuel flow through the carb to cause it to get sucked up into a jet. Now go full throttle and with a 6.2-6.8 fuel flow through the carb and more turbulence that little fleck hits the main jet and slows the fuel and now you have a power loss. This may happen in your first flight or after a few hours. If you pull the throttle back the engine and rpm will smooth back out. This should not cause a loss of the engine, but will certainly get your attention. Don't even think electrical if the power loss happens to you. Just land and pull the carb bowls and find out which might have some debris. No matter how careful you are this could still happen. It did happen to me last week and it was a little fleck of rubber hose the size of a pin head. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 1, 2012 Report Share Posted February 1, 2012 Why don't they have a finger strainer at the carburetor inlet like the one that is on my 1959 Chevrolet pickup truck. That would keep this from happening. Larry Link to comment Share on other sites More sharing options...
Roger Lee Posted February 2, 2012 Report Share Posted February 2, 2012 Hi Larry, It would definitively help, but would be illegal unless you get an LOA. If a mechanic did an inspection technically he would have to make you take it out if it wasn't approved for him to sign off. This happened to me again today. I will from now on blow through the fuel lines I put on before running fuel through them. Most of the time it doesn't happen, but it has happened now 3 times in 22 hose changes and it takes hours to get it fixed. It takes 2 minutes to blow out the lines before I hook up the last one before the carbs. Seems like an easy solution to a problem to me. Link to comment Share on other sites More sharing options...
Rogerck Posted February 2, 2012 Author Report Share Posted February 2, 2012 In addition to blowing out the lines, why not let some wing tank fuel flow through each line before carb hook up? Air might get some debris, liquid some more. Sort of a belt and suspender approach. Roger Kuhn Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 2, 2012 Report Share Posted February 2, 2012 Wow, another one? My question about the finger strainer was not that you or I should add it as an aftermarket item but that Bing should have one on there in the first place. Like I said, my 1959 Chevy Truck has one so it is not an entirely new idea (LOL) Larry Link to comment Share on other sites More sharing options...
Roger Lee Posted February 2, 2012 Report Share Posted February 2, 2012 Hi Larry, It only takes a fleck the size of a pin head to give you grief. There is a screen filter in the fuel pump. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 2, 2012 Report Share Posted February 2, 2012 Yes but that is before the hoses to the carb isn't it? Larry Link to comment Share on other sites More sharing options...
Roger Lee Posted February 2, 2012 Report Share Posted February 2, 2012 Hi Larry, That's true. If the fleck comes from a hose after the fuel pump which I think mine did it's all over, but the crying (and work). Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 2, 2012 Report Share Posted February 2, 2012 Roger, I guess it is true that all things like this come in 3s. Right on target! It ran like a top all the way back to Cottonwood. Idle is pretty slow so in the morning we are going to set the idle and resync. Larry Link to comment Share on other sites More sharing options...
Roger Lee Posted February 2, 2012 Report Share Posted February 2, 2012 Hi Larry, The idle on a cool or cold morning will be a little lower than normal until it gets to operating temps. I just give mine a little extra throttle. Plus you should be warming up at around 2200-2400 to keep the vibration down until metals reach a decent temp. wasn't it set to 1700-1750 upon leaving the other day? If the idle dropped down some it must be the elevation and temp difference between here and there. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 2, 2012 Report Share Posted February 2, 2012 Perhaps it was up there at your elevation but now if I fully idle it is just into the red so I have to be careful til we bump it up. Yes I will do it warm especially since I have a Sheriff Search and rescue mission first thing up near Peach Springs looking for a missing person in a red pickup. Larry Link to comment Share on other sites More sharing options...
hhobbit Posted February 3, 2012 Report Share Posted February 3, 2012 KY jelly? Link to comment Share on other sites More sharing options...
round_peg Posted February 11, 2012 Report Share Posted February 11, 2012 We are still experiencing much grief with tiny bits of rubber in the float bowls and elsewhere in the fuel system (Roger K. and I are the co-owners of this CT). One fairly large piece turned up today in the brass fitting on the fuel line between the carbs. Since it looks to be all but impossible to trace down the source or sources of the rubber bits contaminating the fuel system, we are considering installing a fuel filter in the rubber fuel line between the fuel pump and the carbs. Since there's no rubber upstream of that point, this should catch any further debris. We have an ELSA certificate so we can take this step. I don't know what if anything an SLSA certificated CT could do to address this problem, sort of replacing all the hoses again. Any further suggestions are welcomed. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 11, 2012 Report Share Posted February 11, 2012 Mitch, You are not alone on this issue. Try removing the return fuel line from the top of the gasgalator that is the return line from the carb fuel feed line spreader to the top of the gasgalator and running it into a clean bucket. Run the engine...be careful.. The engine will run with that line removed and allow some fuel to bypass the line that feeds the carbs and pump some fuel into your clean bucket along with the pieces of stuff???? that have collected in that line. You will be able to see that there is a serious amount of those pieces of rubber coming out of that line along with the fuel if you have the same thing going as I do. Let me know what you make out there because it is the same problem that I have been experiencing repeatedly now for two weeks and I would like to further discuss other things that might have some positive results. Of course the last thing that you have to do is remove the float bowls and inspect for the crap in the bottom of them and clean them if necessary. About now I think I have worn out the screws that hold down the intake manifold from the numerous times that I have performed this bowl cleaning process. Twice today alone... There are lots of thoughts on this but the problem never happened before the rubber change. Larry N255CT Link to comment Share on other sites More sharing options...
Roger Lee Posted February 11, 2012 Report Share Posted February 11, 2012 Hi Guys, The rubber change does have a chance of the debris. It is a PITA, but can be rectified. Larry's plane has been a major challenge. I have done over 20 hose changes now and have not had the issue like Larry's. I don't know why Larry's has been any different from all the others. So here is the scoop as they say and the debris can only be in one of two lines. First the fuel comes out of the wings and geos through the first filter in the instrument panel. Then out through the gascolator which has a fine mesh screen. The up to the fuel pump which has a screen inside it. You can see this screen in the gallery pictures. So any rubber particles up to this point are stopped. The only lines that seem to be an issue is only two. The bottom pressure line off the fuel pump up to the carb fuel assembly on the cross over tube and the re-circulation line that comes off there and goes down to the gascolator. I do not know if the re-circulation line goes back in before the mesh screen or after. Either way I don't think that would be an issue because then it has to go back through the fuel pump screen and that is a fine mesh too. This leads me to believe that the culprit is the fuel line off the bottom of the fuel pump. Here may be the next question which I don't have an answer for yet. Could the fuel pump screen catch enough debris from the hose change to clog it during a high fuel demand? The possibility is there, but I don't know how practicable it would be. You would have to have a problem plane that has no other solution then destroy a fuel pump and cut it open. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 11, 2012 Report Share Posted February 11, 2012 First Roger, thanks for calling. I just got your message on my cell and indeed I thought you might have forgotten about me. First, the most troubling part of the debris thing appeared today. After I collected some fuel (as described in the earlier post) with the debris in a clean white bucket I carefully poured off the fuel and collected the particles in a paper towel. When you rub them together with a small amount of dampness from fuel they become just a black spot on the paper towel sort of like you used a felt pen to make the spot. Strange, it seems like the fuel is actually softening the rubber that is flaking off. You (Roger) and I didn't do that when I was down there, they appeared to be hard pieces as they did all the time up to today when I squished them in the gas soaked paper towel. Are the hoses reacting to the alcohol in the fuel??? Don't know. The procedure that I described in the earlier post was performed 3 times today with each time rendering fewer particles. The last time there were no visible particles left in the overboard fuel so we put things back together and performed another float bowl check before test flying. The test flight went OK but I am very concerned that the problem is not solved so flying anywhere except over the airport is out of the question. I don't know of any way to be sure except after several hours of test flights repeat the purge process and see if indeed the problem is solved. Several things are evident to me after the multiple times that we have disassembled and reassembled the various hoses and and carb bowls. The return line that I described in the previous post appears to put fuel back into the gasgalator on the filtered side of the screen. So any foreign material that is introduced into the system after the gasgalator mixes with the returned fuel and is sent to the fuel pump. If that is so then the fuel pump should filter out all debris because everything getting past that point is filtered by the fuel pump. It doesn't seem to do that! On a few earlier trys at a solution I concentrated only on the lines after the fuel pump and purged them with fuel and air, including the hard cross line between the carbs but that solved nothing. So either there is stuff getting through the fuel pump filter or it is introduced after the fuel pump. Neither scenario seems to fit the parameters of the problem that is happening... Still cant trust this thing to fly anywhere. Larry CTSW 255CT Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 11, 2012 Report Share Posted February 11, 2012 Roger, your premise about the fuel pump getting crud in it and causing an insufficient amount of fuel delivered to the engine during high power and consequently high fuel demands I don't believe can be the problem. As you stated... "Here may be the next question which I don't have an answer for yet. Could the fuel pump screen catch enough debris from the hose change to clog it during a high fuel demand? The possibility is there, but I don't know how practicable it would be. You would have to have a problem plane that has no other solution then destroy a fuel pump and cut it open." I think in a previous post you disabled the fuel pump to test whether the engine would quit if the fuel pump quit and I think you determined that the engine would indeed continue to run on enough fuel supplied by the head pressure from the high wing tank. I agree with this. But the fuel had to be coming through the return line backwards out of the gasgalator. If you examine the fuel system you will see that fuel can get to the carbs via the return line backwards from the gasgalator if you totally block the fuel coming from the fuel pump. I don't know any reason for that return line other than to supply an alternate source of fuel to the carbs in the event that the fuel pump fails.... Help me out here but that is the way it looks to me. When we removed the return line from the gasgalator to have it drain while it was running to purge the debris the amount of fuel returning to the gasgalator (now our white bucket) was very small making me think that there is very little reason for that line other than an alternate source of fuel when the fuel pump quits. Larry Link to comment Share on other sites More sharing options...
Roger Lee Posted February 11, 2012 Report Share Posted February 11, 2012 Hi Larry, The re-circulation line is just that. It keeps cooler fuel moving through the lines so you works to help prevent vapor lock from hot lines which may be complicated with altitude. It keeps fuel moving and doesn't let it sit in the line. It does not supply any fuel. I'm still working on answers and I'm definitively talking about this in next weeks Rotax class. Yours has been an exceptional case and I still don't know why. Link to comment Share on other sites More sharing options...
round_peg Posted February 11, 2012 Report Share Posted February 11, 2012 I don't know if our case is any more or less exceptional than the one described by Larry. We have been into the float bowls four times now in two weeks. The problem is certainly not solved and we are no closer than before to understanding its cause. In the meantime I am interested in any reactions to our plan to insert a fuel filter in the line between the fuel pump and the carbs as we are planning on having this done tomorrow. Roger, I hope you can light a fire under the Rotax people, as this issue certainly seems to be the direct result of their maintenance requirements. Link to comment Share on other sites More sharing options...
Flying Bozo Posted February 11, 2012 Report Share Posted February 11, 2012 Roger and Mitch, First, I am permanently grounded until a cause is found! When flying and that thing goes into only half the engine running the other half is running lean and there is a certainty that the lean will burn up that half of the engine. Second, all the cleaning of the system and the float bowls had not removed the problem, only the symptoms. Sure it is cleaned out at that moment but the source of the crap in the fuel has not been addressed and the problem keeps happening. Third, it can't be a plugged up filter in the fuel pump. That would manifest itself as a sagging of power under high fuel demand and not a severe roughness that I am experiencing when this crap in the float bowl appears. Fourth, The only difference from before and now is the replacement of the fuel lines, i.e. the crap has to be coming from them. Mitch, did you experience this after a hose change???? or is this a problem that just popped up randomly? Roger, is this hose the same stuff that is sold at the auto parts store? Roger, can you cut a piece of the new hose that you have, say a few inches of it, lengthwise and then inspect the inside of it when you introduce gasoline to it and see how it reacts? Unleaded with ethanol of course! My next effort is going to be removing the hose out of the fuel pump and cutting it as I described lengthwise and making the test as above. Larry Link to comment Share on other sites More sharing options...
FastEddieB Posted February 11, 2012 Report Share Posted February 11, 2012 I had minor problems with debris when I changed my fuel lines. Being Experimental, adding an additional filter is an option. My plan was to put an inline filter right after the fuel pump*. I went so far as to buy one. I even safety-wired it and put some torque-seal on it in preparation: And it still sits on my workbench, on my "to do" list. BTW, the jets in our carbs are tiny and it takes very little crud to mess things up. This was from my "gasket goop" fiasco, but it still reinforces the point: *on BMW motorcycles using comparable Bing carbs, the drill is to put little inline filters right before the carb. I just Googled "Bing inline filter" to pull up an image, and on the first page was a photo I already posted to this site! Here's a link to that thread, which contains a lot of the above info and relates to this thread: http://ctflier.com/index.php?/topic/655-bing-carb-help-long/ Link to comment Share on other sites More sharing options...
round_peg Posted February 11, 2012 Report Share Posted February 11, 2012 Roger and Mitch,Mitch, did you experience this after a hose change???? or is this a problem that just popped up randomly? Yes, a few hours after the hose change out -- the first time. Float bowls cleaned out, after couple more flight hours, another recurrence. After the fuel system was cleaned out again Friday, we ran it up to full power, static, and all seemed well. I taxied out to fly some patterns. The engine started stumbling on the takeoff run, so I aborted. Turned off, taxied back and did a full-power fast taxi down the runway. Same thing. I did not keep an eye on the tach but I think it probably peaked out around 4,000 RPM. I am very fortunate that the symptoms were manifested on the runway and not on climb-out. The A&P went over the fuel system very throughly and found more debris, including a fairly impressive chunk of rubber (about the size and shape of a fingernail clipping) lodged in the brass fitting where the fuel line from the pump joins the metal tubes between the carbs. It's my understanding that the rubber we are directed to use for this overhaul is an automotive grade part. Is this the source of the problem? I have no idea. Automotive or not, it is fuel line so it certainly should not degrade on contact with fuel. That being the case, the big mystery here is how debris can continue to be generated many hours after the completion of the hose replacement, and after running probably 15-20 gallons of fuel through the system. We will try adding an in-line fuel filter upstream from the fuel pump because it's the next logical step, and our ELSA type certificate allows for the modification. Not in the least happy about this bandaid approach, though. Flight Design and Rotax need to get their heads together on this issue. Every year from now on they will be facing more and more airplanes having this problem and the have to know that it's only a matter of time before someone loses power on takeoff. Link to comment Share on other sites More sharing options...
Roger Lee Posted February 11, 2012 Report Share Posted February 11, 2012 Automotive fuel line is rated for the ethanol just like in our cars. My thinking originally was that the hose when pushed on over the barbed brass fittings may shave off tiny flecks that float down stream. At the request of Larry I have several pieces of fuel line sitting in the fuel, but don't see any debris yet. I still don't have a handle on this and it has happened to several people around the country. I may make a special fuel line with a clear filter in it that goes from the pump (bottom hose on the fuel pump) to the metal fuel assembly on the cross over tube on each hose change. I will install it on each plane and do the carb balance and run ups with the filer in place to be able to monitor and check for debris. When the run ups are all done and if there is no debris I'll remove it. The problem is it may be the very hose that I'll put back on since the fuel pump has a screen. Link to comment Share on other sites More sharing options...
round_peg Posted February 12, 2012 Report Share Posted February 12, 2012 Automotive fuel line is rated for the ethanol just like in our cars. My thinking originally was that the hose when pushed on over the barbed brass fittings may shave off tiny flecks that float down stream. At the request of Larry I have several pieces of fuel line sitting in the fuel, but don't see any debris yet. I still don't have a handle on this and it has happened to several people around the country. I may make a special fuel line with a clear filter in it that goes from the pump (bottom hose on the fuel pump) to the metal fuel assembly on the cross over tube on each hose change. I will install it on each plane and do the carb balance and run ups with the filer in place to be able to monitor and check for debris. When the run ups are all done and if there is no debris I'll remove it. The problem is it may be the very hose that I'll put back on since the fuel pump has a screen. Update: When the A&P cut the fuel line to install the filter Saturday afternoon, he called to report that in his opinion the fuel lines should be replaced. He took a photo which I will post when I get it. Roger, do you know if a milspec fuel line part can be purchased for this application? I don't think we'll want to replace these hoses with another generic off-the-shelf automotive part. I am also becoming skeptical of the value of the inline fuel filter. No matter what you do, some fuel line hose will have to be downstream of the filter. If we are to assume that the hose is the source of the debris then it must be coming from that line since any debris generated from upstream of the fuel pump would be caught by the fuel pump screen. Your suggested diagnostic procedure would not have caught our problem, I don't think, since it took 2-3 hours of flying time after the hoses were replaced for it to be manifested the first time. Also, my sense of this problem is that it has gotten worse/more frequent, recurring more quickly after each float bowl clean-out -- the last time, all of about ten minutes after. If this was a medical condition, it would probably be called "progressive" rather than acute, or even chronic. Also: the A&P has recommended replacing the floats, which seem to flaking off some material. I know he talked to you about this yesterday, and this is what you recommended. Thank you very much for spending this time with him! Link to comment Share on other sites More sharing options...
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