WmInce Posted October 31, 2014 Report Share Posted October 31, 2014 Do you usually remember to close your fuel valve but sometimes leave it open while in the hangar between flights? If left open, that puts static pressure on all fittings, due to head pressure from full tanks. When the fuel is flowing, it does not seem to cause any problem, but sitting statically, I have seen fuel seeping from the gascolator. That valve should always be off when the airplane is sitting. The exception being, when a fuel sample is taken during preflight inspection. Following such a sampling, if the airplane is not subsequently flown, valve should be returned to off. Link to comment Share on other sites More sharing options...
Tom Baker Posted October 31, 2014 Report Share Posted October 31, 2014 If left open, that puts static pressure on all fittings, due to head pressure from full tanks. When the fuel is flowing, it does not seem to cause any problem, but sitting statically, I have seen fuel seeping from the gascolator. That valve should always be off when the airplane is sitting. The exception being, when a fuel sample is taken during preflight inspection. Following such a sampling, if the airplane is not subsequently flown, valve should be returned to off. In my opinion as a mechanic, and you can take it for what it is worth. If you have fuel seeping from the gascolator at any time you should have it looked at, because that is not normal. There are many other high wing aircraft that leave the fuel on all of the time, and they don't have leaking gascolators. Link to comment Share on other sites More sharing options...
sandpiper Posted October 31, 2014 Report Share Posted October 31, 2014 I keep my fuel valve closed when parked, especially inside. Sometimes I forget and have never seen any leakage when this happens. My main reason for keeping it closed when parked is to prevent spillage caused by a carb malfunction. I remember reading something on this forum, or maybe the old one, where someone had this problem. I also keep blocks under my axles when in my hangar. This is in case of a flat with fuller tanks which could cause fuel to leak from the low wing vent. Once in place, I rarely have to adjust them. They stay put and I always park in the exact same spot. I haven't tested to see if fuel would actually leak with a flat. Any volunteers? Link to comment Share on other sites More sharing options...
Anticept Posted October 31, 2014 Report Share Posted October 31, 2014 Seeping fuel from the gascolator isn't normal.Our gascolators may or may not be fitted properly with the curtis drain valves either. When I took my gascolator off earlier this year because of seep, I noticed the rubber seat (it is NOT an o-ring!) on the drain valve was looking a bit torn up. After ordering a new valve (cheap) and putting it on, I saw that the seat was barely rubbing against the threads as ithe valve wasn't fully engaged, there was a quarter inch of threads to go. I took a tap and CAREFULLY rethreaded a bit deeper, and now my drain valve only shows the last thread or so, and it opens into the bowl, rather than into the pipe threading.The gascolator thread sleeve is brass I believe, so when tapping, just do it little by little. A quarter to 8th of a turn at a time, then back off a quarter turn to break loose the little filings. If you don't break the filings loose, it will gall the hell out of the threads and may jam up, increasing the risk of cracking the sleeve. And use a cutting lubricant! Link to comment Share on other sites More sharing options...
Roger Lee Posted October 31, 2014 Report Share Posted October 31, 2014 Hi John, If your tanks are at 15 gals or more and you have a flat you could have some over flow after the fuel transfers. Link to comment Share on other sites More sharing options...
sandpiper Posted October 31, 2014 Report Share Posted October 31, 2014 Hi John, If your tanks are at 15 gals or more and you have a flat you could have some over flow after the fuel transfers. Thanks Roger. I don't often have that much fuel. And, it's been a long time since I've had a flat. But, it only takes once and, as I said, I rarely have to adjust the blocks. How about the carb issue I mentioned? Link to comment Share on other sites More sharing options...
Roger Lee Posted October 31, 2014 Report Share Posted October 31, 2014 First, I'm with Tom and a gascolator should never leak. As far as the carbs go, you should always shut your fuel off when putting it away for the day. Low wing isn't bad, but a high wing will keep constant pressure against the needle valve rubber seat. They can and have leaked. If fuel leaks past the needle valve it will over flow out the vent tube and all over the floor. I have seen it a few times. So it is just as easy to get in the good habit of turning the fuel off. Link to comment Share on other sites More sharing options...
WmInce Posted November 1, 2014 Report Share Posted November 1, 2014 In my opinion as a mechanic, and you can take it for what it is worth. If you have fuel seeping from the gascolator at any time you should have it looked at, because that is not normal. There are many other high wing aircraft that leave the fuel on all of the time, and they don't have leaking gascolators. Thanks to all. Will have it checked out immediately. Link to comment Share on other sites More sharing options...
207WF Posted November 12, 2014 Report Share Posted November 12, 2014 My carbs have soiled the trays, on and off, for most of their lives. Right now one side is staying clean and the other drips a bit. It has always been a persistent and recurring nuisance. Have tried everything, rebuilt the carbs twice, replaced one carb with a new one, etc. I might get them to stay clean for a while, but it always comes back. By now I am sort of getting used to it (1050 hours). I monitor and when it gets too bad, take action one more time... WF Link to comment Share on other sites More sharing options...
Matt Posted July 12, 2015 Report Share Posted July 12, 2015 First, I'm with Tom and a gascolator should never leak. As far as the carbs go, you should always shut your fuel off when putting it away for the day. Low wing isn't bad, but a high wing will keep constant pressure against the needle valve rubber seat. They can and have leaked. If fuel leaks past the needle valve it will over flow out the vent tube and all over the floor. I have seen it a few times. So it is just as easy to get in the good habit of turning the fuel off. Hi Roger, Thank you for all your good posts. I'm a passive reader but it helps me with flying my CTLS. Things like "follow the ball" for fuel tank distribution works for me... Regarding the carbs comment... I flew for about 3.5 hours yesterday and all fine. The engine never runs rough - idle or with power. All good. Here is my question for a comment to check if anyone else with a CT has such occurrences: Today, in the hangar I pushed the tail down and hence the nose went up and I heard this fluid flow noise onto the floor – like a little open tap. It was fuel flowing from under the cowl and it came out of the airbox venting tube that drains next to oil and fuel pump vents. It seems the fuel must have sat in the carby and due to the nose going up drained into the airbox via its venting tube and then exited via the airbox venting tubes. It was not just a couple of drops but more like about 50 to 100 ml. After inspection I lifted the nose again as before and few more drops continued fast until it stopped. I had left the fuel tap open overnight. The engine has about 130 hours on it and I'm not easily willing to take the carburetors off and check them for faulty valves or bad floats - (The Rotax SBs last year do not apply according to my part numbers). I need to have my licensed mechanic do something, but just checking whether anyone else has experienced this - as in not just a few drops but a flow, only when changing the planes attitude on the ground by pushing down the tail causing fuel to flow out of the venting tube. Thanks for any comments, Matt Link to comment Share on other sites More sharing options...
FastEddieB Posted July 12, 2015 Report Share Posted July 12, 2015 There's a needle and seat that is controlled by the floats. From my BING experience, you may have... 1) A small piece of crud in the seat, or damage to the "needle" tip, preventing it from fully stopping the flow of fuel. Easy to check functionally by removing the float bowl and gently holding up the arm that the floats bear against. With the fuel valve ON, gentle pressure should completely stop the flow of fuel. May also want to drive out the pivot pin to make a visual inspection of the needle and seat. Once the needle is out, it may take a mirror and a bright light to look up into the valve seat to make sure it's clear. If there's crud up there, a little shot of compressed air may blow it out. It does not take much to hold it open. Here's what the "needle" looks like: 2) The floats may be too heavy. Easy to weigh them. I think the maximum for the pair is 7 grams - there a ROTAX Service Bulletin that's been linked to before. #2 is not likely if you're not in the range, but it's very easy to check. #1 should not involve pulling the carbs, as long as the float bowls can come off with the carbs in place. In any event, this should be seen as a big deal - you don't want fuel loose in the engine compartment, drip trays or not! Link to comment Share on other sites More sharing options...
Roger Lee Posted July 12, 2015 Report Share Posted July 12, 2015 You have one of three issues in the carbs. 1. Heavy floats allowing the fuel level to be too high, but since your idle isn't rough then this may not be it. 2. As Eddie points out it is possible to have a damaged needle valve. This would require you to remove the carb to check. 3. The carb float armature that controls the float height is slightly tweaked and allowing the fuel level to be a little too high. The carbs have to come off to adjust them. Since the fuel isn't only in the drip tray then it isn't a bad bowl gasket. My number one guess is since you left the fuel valve open (should always be turned off when storing the plane on a high wing) the fuel in your high wing had just enough pressure to leak past the needle valve. It isn't a big problem, but you need to get in the habit of shutting off the fuel overnight. Link to comment Share on other sites More sharing options...
Tom Baker Posted July 12, 2015 Report Share Posted July 12, 2015 If you had that much excess fuel in the carbs make certain that you turn the engine over by hand through several compression strokes to make sure it isn't hydro locked. Link to comment Share on other sites More sharing options...
gbigs Posted July 12, 2015 Report Share Posted July 12, 2015 Burping should be done before EACH flight, but that won't fix a fuel leak... If you are spilling fuel just tilting the tail down have a mechanic check it out before flying again... Link to comment Share on other sites More sharing options...
Roger Lee Posted July 12, 2015 Report Share Posted July 12, 2015 Hydro lock in some Rotax engines is overstated and is a holdover from yesteryear. Fuel won't ever be an issue for hydro lock because it would take a ton of fuel from most likely a high wing and if that much fuel could flow from a carb towards a cylinder to fill it up it will be all over the ground because the fuel would flow both ways. Fuel has never really been an issue. If you have a fuel valve it should always be off when not using your plane. Oil hydro lock comes from a couple of issues from years ago. The KitFox was the major offender and anyone with a high mounted oil tank. (Overly low mounted tanks presented a different issue) The oil tank has a spec for its mounting height compared to the engine height. KitFox used to mount the tanks way too high out of spec. The old oil filters did not have a check valve and the old anti drain back membrane was stiffer and didn't do as good a job to prevent the drain back. When you add these things together there was a chance that some oil could seep through after a long period of sitting and partially fill a cylinder. This wouldn't happen if you let it sit for an hour to eat breakfast. This took some real time. With the newer filters and more people paying attention to the mounting specs there is only a minute chance for this now. If I owned a Kitfox I would still always check. With a properly mounted oil tank this situation is greatly reduced. I haven't even heard of one for many years. I'm not telling anyone how to use there engine, but this info is just to fill in the blank spots. Link to comment Share on other sites More sharing options...
Tom Baker Posted July 12, 2015 Report Share Posted July 12, 2015 Roger, I only mentioned it, because he has a high wing airplane and there seemed to be a lot of fuel by his account. I want to error on the side of caution, and it is a simple measure to take to prevent any possible problems. Link to comment Share on other sites More sharing options...
Roger Lee Posted July 12, 2015 Report Share Posted July 12, 2015 Hi Tom, It wasn't directed at anyone for any reason. Just thought I would add a little background info. Link to comment Share on other sites More sharing options...
Matt Posted July 13, 2015 Report Share Posted July 13, 2015 Hi Eddie, Roger, Tom, Many thanks for your fast responses. This is valuable info I really appreciate and great we have a global forum to discuss. As suggested by Roger I will make sure to always switch off the fuel valve - my mechanic suggested this also after discussion. Will monitor whether I have a similar "leak" then. Thanks all, Matt Link to comment Share on other sites More sharing options...
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