Philip Welsch Posted March 27, 2012 Report Share Posted March 27, 2012 Winter blend gas in summer air temps ? PRW Link to comment Share on other sites More sharing options...
Roger Lee Posted March 27, 2012 Report Share Posted March 27, 2012 I believe it is 1/4" NPT. For those that worry about filtering their fuel. You have a strainer (they call it a filter, but the holes are huge) in each wing, then the fuel goes through the fuel filter in the instrument panel, then through the gascolator (fine mesh screen), then the fuel pump which has a screen and then the re-circulation line going back to the gascolator goes back in on the upstream side which means it has to go back through the gascolator again. For those that have ask the re-circulation line that goes back to the gascolator gets filtered again. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 27, 2012 Author Report Share Posted March 27, 2012 Winter blend gas in summer air temps ? Maybe... winter changes to summer quickly here. -Russ Link to comment Share on other sites More sharing options...
Tom Baker Posted March 27, 2012 Report Share Posted March 27, 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 If it was me I would just put on a longer new hose, or pull the hose off the old fuel pump. If you had known ahead of time you could have pulled the hose off the fuel pump and kept it hooked up to the gascolator. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 27, 2012 Author Report Share Posted March 27, 2012 If it was me I would just put on a longer new hose, or pull the hose off the old fuel pump. If you had known ahead of time you could have pulled the hose off the fuel pump and kept it hooked up to the gascolator. Yeah, that's the route I'm going to take. The old hose needed replacing anyway (five years old), so I'm just ordering a new one. -Russ Link to comment Share on other sites More sharing options...
GlennM Posted March 27, 2012 Report Share Posted March 27, 2012 I am with Roger, why is your airplane the only one that has this problem? It seems to me you are only treating the symptoms by switching fuels. I think you are looking for a restriction upstream of the gascolator. A collapsing fuel line upstream of the gascolator? Since the fuel should not vapor lock with gravity, I would think the draw of the fuel pump is more likely. I think upstream of the gascolator since you said bubbles were coming out of it. I would check the flow at various points along the fuel system from tank to carb. Link to comment Share on other sites More sharing options...
GlennM Posted March 27, 2012 Report Share Posted March 27, 2012 I posted the above reply before I read Roger's description of the CT fuel system. I did not realize there was a recirculation line. You might have a restriction or blockage of your fuel recirculation line. Years ago, I mis-piped a fuel distributor by leaving the recirculation line off (the distributor was capped). It was discovered by a really high fuel temp (in excess of 400F - it was jet fuel and the alarms were ringing). Without the recirculation line, the fuel flow was low enough at idle that most of the work the pump was putting into the fuel to pump it was causing it to heat up since it was dead headed. The hotter fuel vapor locks easier. It is worth a check. Link to comment Share on other sites More sharing options...
Russell Croman Posted March 28, 2012 Author Report Share Posted March 28, 2012 I have pretty thoroughly checked for any restrictions in the fuel system. One check was draining fuel from the gascolator and measuring the flow rate... 19.2 gph... far more than the engine can draw. Unless fuel can be drawn faster than this, the pressure in the lines going from tanks to the gascolator (including the fuel valve and filter) cannot drop below atmospheric, and so can't collapse. The fuel pump has been replaced, along with both of its hoses. The fuel intake line is (I think) the only one under suction during operation, so would be the only one susceptible to collapse. With the fuel lines disconnected from the carbs, fuel flows freely out of them by gravity when the fuel valve is open. I checked the recirculation line by disconnecting it from the fuel distributor and opening the fuel valve... fuel flows freely from it by gravity as well. I also checked the restrictor in the recirculation line banjo fitting for debris... it's clean. I also checked for any leaks in the fuel system downstream of the fuel valve by hooking up a small hand pump to the fuel distributor (where a pressure sender would go), closing the fuel valve, and pumping it up a bit. No leaks. I did this to test the theory that air was getting into the fuel loop somehow via a small leak. I checked the gascolator screen (it was very clean except for a few tiny bits of lint). All of the above plus these observations: - I never had any engine trouble unless it had first been run (warmed up), then stopped or taxied for several minutes, then run at full throttle for takeoff or climb out. - The carburetors have been cleaned (multiple times) and finally rebuilt. Nothing I ever tried with the carbs made any difference. - The fuel pressure (measured by mechanical gauge) was stable when the engine was cold, but always got erratic once the engine got warm. - At full throttle with E10 fuel with a warm engine, the fuel pressure would drop to zero on the takeoff roll, followed by the engine sagging as it leaned out (float bowls emptying out), and finally stumbling as it ran out of fuel. - At full throttle with 100LL, the (less) erratic fuel pressure steadies out on the takeoff roll and stabilizes at ~4psi, just like described in this thread, and the engine doesn't lose power on the takeoff run. I also spoke with a rep at Lockwood and he mentioned that vapor lock has been seen on some CTs, but only when using fuel with ethanol in it. Everything is consistent with vapor lock, and I've not observed anything that contradicts that conclusion. That being said, whether the higher vapor pressure fuel is the cause or just a contributor is indeed not certain. I only know that E10 does definitely have higher vapor pressure (evaporates more easily) than 100LL, and switching to 100LL seems to have cured the issue. What else could be wrong in the fuel system that could cause this? I'm open to ideas. The fuel system is rather simple, actually... I can't think of any part of it I haven't either thoroughly checked or outright replaced. Also, what is different about my 2006 CTSW (serial 06-09-09) that makes the fuel pump intake line too short? Was the gascolator moved on later planes, perhaps to get it further away from heat sources to help prevent vapor lock? (I confirmed today with Lockwood that they have seen the short intake line issue on a few early 2006 planes.) Perhaps there is something peculiar about the fuel system arrangment on this plane? -Russ Link to comment Share on other sites More sharing options...
Tom Baker Posted March 28, 2012 Report Share Posted March 28, 2012 Russ, every new rotax fuel pump I have bought has had the same line on it. It is a standard Rotax part. They don't know what airplane it is going on when it is made. The fuel strainer is located in the same spot on all of the CT's I've worked on. For airplanes with the dual Dynon set up the is a connection at the fuel pressure damper on top of the engine and you have to cut the hose off to make the connection. For airplanes with analog instruments the line goes straight from the fuel pump to the fuel strainer, and it is to short. I have seen airplanes that have had a one piece hose put on at the factory, and I have seen them with a factory splice 10-12 inches from the strainer. Tom Link to comment Share on other sites More sharing options...
Russell Croman Posted March 28, 2012 Author Report Share Posted March 28, 2012 Thanks for the info, Tom. -Russ Link to comment Share on other sites More sharing options...
opticsguy Posted April 9, 2012 Report Share Posted April 9, 2012 Russell, You might want to check about the intermittent ignition modules. It's the only thing that can describe my symptoms as of now. I heard from a reliable source that this has happened 4-5 times to 2006-era Rotax installs. Link to comment Share on other sites More sharing options...
Russell Croman Posted April 10, 2012 Author Report Share Posted April 10, 2012 Since draining out the winter blend car gas + ethanol and replacing with avgas, I have flown for about 15 hours in Texas heat with zero engine issues. -Russ Link to comment Share on other sites More sharing options...
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