Russell Croman Posted March 3, 2012 Report Share Posted March 3, 2012 Hi folks, I'm a new owner of an '06 CTSW, and also a new pilot... just did my first solo two days ago. Yesterday I did my second solo and had engine trouble. At about 250' after takeoff the engine started a sort of oscillation between about 4000 and 5000 rpm, maybe a little faster than once a second, dropping off and then surging back to life. I started looking for a field to make an emergency landing in, but also pulled the throttle back a bit and the engine smoothed out, for a few seconds anyway. Going back to full power, it ran okay for a few seconds, then started surging again. Fortunately there was enough power through all of this that I was still climbing. At maybe 800' I made the turn downwind and brought it around in a tight pattern to a safe landing. After changing my shorts, conferring with my instructor, and popping the cowl to look for anything obvious with a (non-Rotax) mechanic nearby (e.g., balance tube came off or something), we did a couple of high-speed taxis at full power and it ran just fine. We took off together and climbed out over the runway. After several minutes, it did it again. Just one surge, but it was enough to rule out trying to fly it back to our home airport. We landed it and tied it down, and it's now waiting to be serviced. The engine did this once before, right after I purchased the plane. A buddy and I flew it down to Sebring and went to the Sport Expo while the ELT got upgraded and a leaky valve cover was fixed. Carb sync and idle adjustment were also performed. When we took off to fly it back to Texas, the engine did the same thing after maybe four minutes of climbing. Again it would steady out a bit, but not completely, if I reduced power a little. We returned to Sebring, had the mechanic look it over, drained some fuel to make sure it was clean, and found nothing. I chalked it up to having forgotten to sump the fuel during the preflight. We took off again and it ran just fine for the next 20 hours, until yesterday. Any ideas on what could cause this? Here's a link to the cockpit video... the surging starts at about 0:40. No audio, but you can see the tach fluctuating. Thanks, Russ N296CT Link to comment Share on other sites More sharing options...
markmn Posted March 3, 2012 Report Share Posted March 3, 2012 Likely fuel related. Do you have a fuel pressure guage? There have been plenty of fuel pump issues on the 912 rotax. I have had the same experience in my tecnam (losing power on takeoff)more than once and it is an eye opener to say the least. My problem ended up being a faulty fuel pump. My fuel pump would destroke in very cold winter weather here in MN. I tried three new pumps and all three would fail in temps below 15F but would work fine as soon as temps rose. I now have the new style pump and have had no problems this winter. Mark Link to comment Share on other sites More sharing options...
Roger Lee Posted March 3, 2012 Report Share Posted March 3, 2012 Hi Russell, You have a fuel flow issue. Might be the pump, but not usually. You need to drop the carb bowls and take a look. See when you are throttled back there isn't much fuel flow or turbulence in the bowl. At full throttle or close to it you have a lot of flow and more turbulence. What ever is floating around in the bowl starts moving and follows the current up to the main jet. If you don't see anything in the bowl I would pull the carbs and flush them with some cleaner and back it up with some air. If you have a Dynon then you can look at the fuel pressure. If the plane has just gone through a rubber hose replacement then it is some debris from the hose. You will still need to pull the carbs. I know you may not want to pull the carbs, but you will spend huge amounts of wasted time hoping it isn't the problem. Better just do it and be done with it and save the time. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 3, 2012 Author Report Share Posted March 3, 2012 Thanks for the info, guys. Roger, if we drop the carb bowls and find hose debris or other junk, is it sufficient to just clean the bowls and re-install? In other words, do we only need to pull the carbs if we don't find junk in the bowls? -Russ Link to comment Share on other sites More sharing options...
Roger Lee Posted March 3, 2012 Report Share Posted March 3, 2012 If you find something in the bowls and remove it, it is not a 100% guarantee it's all gone. Fly it and find out or run it full throttle on the ground for 5 minutes. If it is still there then you will need to remove and flush the carbs. I doubt this is a fuel pump, but it needs to be ruled out. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 4, 2012 Author Report Share Posted March 4, 2012 Well, sure enough, there was a bunch of junk in the carb bowls (not the penny... that's just there for scale)... Some of this was adhered to the bottoms of the bowls, but a good amount of it was loose. There were also a couple of very small black flecks (that didn't make it into the photo) that might have been hose debris. The engine had a partial hose replacement about 50 hours ago. After cleaning the bowls out with fresh fuel and reinstalling, it started up just fine. I warmed it up and then did a few minutes at full throttle as suggested. Couldn't go longer due to the oil temp getting too high, so I let it cool a bit and then did it again for a few minutes: no faltering. My instructor and I will now test fly it, hopefully tomorrow. So the big question in my mind is what is this stuff and how did it get in there? The bigger pieces crumbled easily between fingers into a fine powder. Some sort of sediment build-up? One mechanic I spoke with thought it might be residue from evaporation of mogas with ethanol in it, but I'm not convinced. The previous owners used ethanol-free mogas the whole time they had it. I've been using mogas with about 7% ethanol in it because it's all I can get, but that's only been for about 20 hours of operation. There was also evidence of some pitting in the bottoms of the carb bowls (sorry, no picture). Could there be something in the fuel that is corroding the bowl, leaving this residue? -Russ Link to comment Share on other sites More sharing options...
josjonkers Posted March 4, 2012 Report Share Posted March 4, 2012 Well, sure enough, there was a bunch of junk in the carb bowls (not the penny... that's just there for scale)... Some of this was adhered to the bottoms of the bowls, but a good amount of it was loose. There were also a couple of very small black flecks (that didn't make it into the photo) that might have been hose debris. The engine had a partial hose replacement about 50 hours ago. After cleaning the bowls out with fresh fuel and reinstalling, it started up just fine. I warmed it up and then did a few minutes at full throttle as suggested. Couldn't go longer due to the oil temp getting too high, so I let it cool a bit and then did it again for a few minutes: no faltering. My instructor and I will now test fly it, hopefully tomorrow. So the big question in my mind is what is this stuff and how did it get in there? The bigger pieces crumbled easily between fingers into a fine powder. Some sort of sediment build-up? One mechanic I spoke with thought it might be residue from evaporation of mogas with ethanol in it, but I'm not convinced. The previous owners used ethanol-free mogas the whole time they had it. I've been using mogas with about 7% ethanol in it because it's all I can get, but that's only been for about 20 hours of operation. There was also evidence of some pitting in the bottoms of the carb bowls (sorry, no picture). Could there be something in the fuel that is corroding the bowl, leaving this residue? -Russ Looks like you had a "Lincoln" size problem in your carbs. Link to comment Share on other sites More sharing options...
FastEddieB Posted March 4, 2012 Report Share Posted March 4, 2012 From my experience with the same basic carbs on motorcycles, water in the fuel will settle to the lowest point - any getting in the carb will sit in the bottom of the float bowl and can cause oxidation. I also had some freeze in a float bowl and hold the float up and prevent fuel from flowing. Of course, water should be sumped out at a gascolator or equivalent, but some may get by in suspension, or could even condense from humid air in the bowl itself. Just my guess, but consistent with the pitting. Could the crumbly bits have been oxidized aluminum? Link to comment Share on other sites More sharing options...
Roger Lee Posted March 4, 2012 Report Share Posted March 4, 2012 I blew the picture up and with the pitting description it is indeed from water sitting in the bowl. The black small pieces was probably pieces of hose. Unless this contamination got up into a jet you should be done. If it does it again tomorrow the carbs have to come off and get flushed. If you use fuel with ethanol you won't have the water sitting in the bottom of the bowl causing this and the water trapped in the fuel will just burn through the system. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 5, 2012 Author Report Share Posted March 5, 2012 No joy. Engine runs just fine on the ground, even at full throttle for minutes. As soon as we got to about 500', the engine sagged and then came back... same behavior. I guess it's carb cleaning time. -Russ Link to comment Share on other sites More sharing options...
Safety Officer Posted March 5, 2012 Report Share Posted March 5, 2012 Have you checked the fuel pressure with a mechanical gauge and checked the fuel filter? The carbs still need to be done, but you should rule these out as well. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 5, 2012 Author Report Share Posted March 5, 2012 Haven't checked those yet... the plane unfortunately is now stranded at an airport away from my mechanic. And it doesn't have a fuel pressure gauge installed. I noticed when I sumped the fuel today that there were some little white particles in it. I had seen this before, but had assumed it was lint or something in the container, not in the fuel. But I kept going today and sumped it multiple times, and kept seeing a few particles each time. I am wondering if this could be clogging up the fuel filter and leading to a loss of pressure at full throttle. I'm tempted to drain all of the fuel, put a few gallons of 100LL in, rock the wings to swish it around, and drain it again, just to flush any crud out... before we do the carbs. I'd hate to get them all clean and then just run a bunch of junk back into them. Actually, could a clogged fuel filter be the answer? What happens when the carbs can't get enough fuel? Wouldn't the engine sag as the bowls empty out, but then come back as the bowls filled again? And wouldn't this cycle tend to repeat at full throttle, but perhaps smooth out at lower power settings? That's pretty much the pattern I observe. -Russ Link to comment Share on other sites More sharing options...
WmInce Posted March 5, 2012 Report Share Posted March 5, 2012 Any slight possibility of fuel contamination? Before retesting, was the old fuel purged and the tank refilled from a different source? Link to comment Share on other sites More sharing options...
Tad Olmsted Posted March 7, 2012 Report Share Posted March 7, 2012 check the fuel pressure at WOT on the ground. If you do not have a Dynon, there is a port at the back of the fuel metering block located at the top of your engine clamped onto the aluminum compensating tube. Remove the plug and slave in a mechanical gauge and tie it up tight so you can see it in the cockpit for your runs. I suspect you have a combination of fuel restriction and/or trash in the lines, tanks, gascolator etc... Link to comment Share on other sites More sharing options...
Russell Croman Posted March 7, 2012 Author Report Share Posted March 7, 2012 Thanks for the info. Here is my plan of attack: 1) Check the fuel flow rate out of the gascolator (should be > 9.25 gph) If bad, check fuel filter and gascolator for blockage 2) Check the fuel pressure at all throttle settings, especially wide open If bad, does this necessarily mean a bad fuel pump? 3) If fuel flow and fuel pressure check out good, pull the carbs and clean them -Russ Link to comment Share on other sites More sharing options...
Roger Lee Posted March 8, 2012 Report Share Posted March 8, 2012 The gascolator will take two minutes to check. I would just do it. Put your mechanical 0-10 psi gauge on to check the pump pressure. Then my bet is you are going to pull the carbs and everything will be back to normal. The reason I say it this way is that it runs fine on the ground, but as soon as you change the float orientation and fuel turbulence in the float bowls is when something gets reduced. Since it runs at WOT on the ground you could actually rule out the gascolator and fuel pump pressure or it would cough and stutter on the ground too. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 23, 2012 Author Report Share Posted March 23, 2012 I have now had both carbs rebuilt and replaced the fuel pump. No joy. The signature is slightly different however. I did a bunch of high-speed taxis after getting everything back together. When I first go to full throttle with the brakes on, the rpm goes smoothly to 4950 or so and stays put as long as I am not moving. I can sit there like that for minutes and it will just run rock steady. When I release the brakes and start to get some airspeed, the rpm starts to drop. Most of the time it fell smoothly to about 4700 and stayed there until it was time to throttle back. On the last run, however, it continued to sag and then stumbled as it had before during flight. Again it smoothed up as soon as I backed off the throttle. This all happened without getting into a nose-high attitude. It seems more related to airspeed than acceleration (I.e., it didn't sag right away when I released the brakes). This seems very much like a fuel flow issue... it seems like it's leaning out when in motion for whatever reason. I have checked the fuel drain rate out of the gascolator... 19.2 gph. When I put the new fuel pump on but hadn't yet attached the fuel lines to the carbs, I opened the fuel valve to check, and fuel flowed freely out of the lines. If it's not the carbs and not the fuel pump (which included new fuel lines), what could it be? -Russ Link to comment Share on other sites More sharing options...
Roger Lee Posted March 23, 2012 Report Share Posted March 23, 2012 If a hose has been changed before this happened someone may have put a Band-It clamp on too tight. Pull the bowls again and look. I hope whom ever did the carb re-build set the float arm level properly? When you accelerate or pitch the nose up that may change the float position just enough to cause it to cough. It is possible it is the floats. Did you do a mechanical fuel pressure check? Link to comment Share on other sites More sharing options...
Russell Croman Posted March 23, 2012 Author Report Share Posted March 23, 2012 Hoses were changed a year ago. What would I look for in the bowls? Floats are brand new w/ the rebuild. Not sure on the float arm level check, but they were rebuilt at Lockwood... I'll check tomorrow. No fuel pressure check yet... I'll have to install a temporary gauge. -Russ Link to comment Share on other sites More sharing options...
Russell Croman Posted March 26, 2012 Author Report Share Posted March 26, 2012 Vapor lock. I am 90% certain this is what I have been fighting all along. Hooking up a mechanical fuel pressure gauge, on the first start of the day, the pressure initially looks great... steady around 4psi. After warming up the engine, I shut it down, wait five minutes, and start it up again. Now the pressure has dropped to under 3psi and fluctuates widely, going as low as 0psi at times. Very much as described in this thread, except that it doesn't clear up as more fuel is circulated into the system. Rather, it gets worse. On a high speed taxi, it goes even lower and stays at 0psi for seconds at a stretch. Eventuallly the float bowls empty, the engine leans out and finally stumbles. Throttling back always clears it up, since there is some flow into the carbs, just not enough to keep up with takeoff demands. The clincher was shutting down the engine while the pressure fluctuation was going on and popping open the gascolator valve... bubbles! Lots and lots of bubbles, and the fuel was almost hot to the touch. Then after a few seconds the bubbles stop and cooler fuel starts coming out, fed from the wing tanks. I did this multiple times just to make sure I wasn't seeing air trapped in the system or something. I have been running straight mogas with ethanol in it, which forms vapor more easily than 100LL. So as a test I drained most of the mogas and replaced it with 100LL. Voila! The fuel pressure fluctuations were much less, never dropped below 2psi, and also now went away completely after a few seconds at takeoff power, stabilizing at 3-4psi as the vapor cleared out of the system. Maybe I got a bad batch of mogas or something, with an abnormally high vapor pressure. Who knows. Despite the maintenance trade-offs, I am switching to 100LL. -Russ Link to comment Share on other sites More sharing options...
Roger Lee Posted March 26, 2012 Report Share Posted March 26, 2012 Hi Russell, Run away from 100L. It does more damage than you think. It isn't just added maint. cost up front, but later is a big issue. Just like in the air cooled GA engines, 100LL isn't good. Fix the cause of the vapor lock. I would also have a hard time believing it is vapor lock since you just start the engine and taxi and you get vapor lock right away, unless you spend a lot of time on the ground and build too much heat. The rest of us don't have this issue as you do so you need to fix the cause. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 26, 2012 Author Report Share Posted March 26, 2012 Sorry, ethanol is what I am running away from at the moment. And mogas w/o ethanol is simply not available in my area. Mogas has vapor pressure specifications, but apparently they are relaxed when ethanol is added. I know this is a controversial issue, so let's just leave it at that. I take full responsibility for all effects of the fuel I put in my plane, and I will be completely forthcoming with any future buyer. I am open to the idea that something else could be contributing to the vapor lock. I checked the fuel system for leaks downstream of the fuel valve today... all good. So I don't think air is getting sucked in anywhere. What are other possible causes? Here's one detail: the new fuel pump I got (with hoses attached) has an intake line that is too short to reach the gascolator when the hose is routed behind the motor mount. I had to route it within a couple of inches of an exhaust pipe to get it to reach. Has anyone else had this issue with the new fuel pumps (part #893-114)? -Russ P.S. Note that this hose routing is definitely not the cause of the trouble. The fuel pump was just replaced last week... the trouble has been going on much longer, with the same observed fuel pressure issues. Link to comment Share on other sites More sharing options...
Roger Lee Posted March 26, 2012 Report Share Posted March 26, 2012 Hi Russ, The majority of us run 91 oct. with ethanol. We have been for years. Somewhere in your system something is causing you grief. It may be a hose too close to something hot or an unprotected hose. Possible even a hose with a fire sleeve clamp too tight that is restricting flow? There are CT's in the world that are more than double the ethanol we have here without any issues. Where do you live? Maybe there is someone not too far that really understands the CT and its fuel system. Link to comment Share on other sites More sharing options...
Tom Baker Posted March 26, 2012 Report Share Posted March 26, 2012 The hose for the airplanes with analog instruments is to short. You either have to splice the hose, or replace the whole section. I have seen both in factory installations. You should correct the hose length and go back to the routing over the top of the engine. For airplanes with the Dynon you have to cut the hose for a connetion on top of the engine. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 26, 2012 Author Report Share Posted March 26, 2012 Does anyone know the thread specs on the gascolator elbow fitting that goes to the fuel pump intake line? I think it's NPT something... maybe 1/4"? What if I stack a couple of adapters of that thread to extend the gascolator fitting to reach the hose? Seems easier than splicing the hose. -Russ Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.