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  #11  
Old 12-19-2017, 07:59 AM
vic syracuse vic syracuse is offline
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Quote:
Originally Posted by DanH View Post
In addition to a trash check in the float bowls, note that Bings can be blocked with a flake of trash in the fuel inlet, upstream of the float needle.
I have seen more than one Rotax 912 exhibit these symptoms and it is usually trash in the carb bowls that is blocking the jet, or as Dan says.

Vic
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  #12  
Old 12-19-2017, 08:11 AM
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Phantom30 Phantom30 is offline
 
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I just went through this dance...except I was losing fuel psi. Found a ball of shredded plastic shavings in fuel line fitting coming out of engine fuel pump.

With your pressure reading normal; id pull the individual fuel lines to each carb and inspect (along with carb obstructions within the carb)..

The material looked like the inside of the fuel hose...could have been caused when fittings were installed as it was nothing that could have made it through the gasolator.
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  #13  
Old 12-19-2017, 01:20 PM
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RV10inOz RV10inOz is offline
 
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Besides the obvious debris in the carb, check the balance tube between the two carbs. I have seen blockage/crimped as well as worn through to a hole.

Next big one is ignition, did you do a mag check, or an ignition pack check. One could be faulty or just loose wiring to the pack. This is where 4 x EGT probes is more diagnostic than the two collector averages.
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  #14  
Old 12-19-2017, 01:59 PM
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scottmillhouse scottmillhouse is offline
 
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Default Could be fixed

Thanks for everyone's input. It kept me focused to carb obstructions. Went back out today. Ran compression all great. Pulled both carbs. Zero trash in bowls, no jet restrictions. Disconnected lines and flushed, reconnected and flushed through carb. Reassembled and engine runs fine. Once warm ground static up to 5000 rpm like before. Did not see any trash but it is possible that something got dislodged when flushing. Did not balance carbs or fly due to rain. Will repeat and rebalance carbs, install cowl and do some high airport circuits to test before I trust it. Wish there was visible cause so I know it is fixed.

To complete the post. I ran the engine up twice with all ok and then reassembled to fly. Once again power reduction. With our weather it sat again for about another 2 weeks. I disassembled everything, flushed and removed all auto fuel, filled tank with 100 LL and flushed again. Reassembled and flew today. A few circuits high above my airport and then at altitude in area. All worked great with EGTs matching. I think this was a fuel issue. Filled for a Xcountry that never happened and it aged with wide temperature swings with only a couple of short flights.

Update: After flying the last couple of months with 100LL, absolutely no problem. Assumed alcohol in aged auto fuel created a blockage in lines. Will go back to auto fuel when weather turns and I can fly at least weekly. I learned my lesson and will switch to 100LL for winter from now on.
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Last edited by scottmillhouse : 03-11-2018 at 01:07 PM. Reason: update
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  #15  
Old 12-19-2017, 06:21 PM
XPPilot XPPilot is offline
 
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Default In flight Rotax power loss

I experienced the same couple of months ago. Just before it I replaced fuel lines and particle ended to carb bowl.

As an end result of that I ended up to overhauling carbs and flushing fuel system. Like said, it takes tiny flake to restrict fuel flow and engine is shaking due to unbalanced fuel flow to both sides of the engine.

In my case it took couple of hours to build trust back to the engine.

Have any of you converted your fuel lines to braided stainless steel PTFE fuel lines? With Teflon lines you don't have to worry ethanol and replacing those all the time.
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  #16  
Old 12-19-2017, 09:57 PM
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Phantom30 Phantom30 is offline
 
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Quote:
Originally Posted by XPPilot View Post
I experienced the same couple of months ago. Just before it I replaced fuel lines and particle ended to carb bowl.

As an end result of that I ended up to overhauling carbs and flushing fuel system. Like said, it takes tiny flake to restrict fuel flow and engine is shaking due to unbalanced fuel flow to both sides of the engine.

In my case it took couple of hours to build trust back to the engine.

Have any of you converted your fuel lines to braided stainless steel PTFE fuel lines? With Teflon lines you don't have to worry ethanol and replacing those all the time.
After finding the ball of shredded plastic looking stuff that looked like the inside of the fuel lines that came with engine...I just eplaced with the kit that Aircraft Specialty sells (really nice setup (all Teflon/Braided SS w/AN fittings)..will not have to worry about 5 year change-out.
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  #17  
Old 12-20-2017, 06:54 AM
Aircraft Specialty Aircraft Specialty is offline
 
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Ric and All,

The RV-12 Conductive Teflon fuel line retrofit kit is currently on between 60-70 RV-12 aircraft as well as a variety of other 912 powered aircraft.

It was originally designed as a replacement to the rubber hoses that were being supplied with the engines. We had many customers call and ask us to design a system that used conductive Teflon instead of rubber. It provided a cost effective alternative at the 5 year replacement mark for a hose package that did not need to be changed out at 5 year intervals.

Ric's old hoses are currently enroute to us and we will dissect them once they arrive and see what we find.

Steve

P.S. As a side note, we are still collecting data, but we have not had any complaints (utilizing our fuel system) of the sporadic low fuel pressure indications that seem to affect some of the rv-12 utilizing the stock fuel system.
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Last edited by Aircraft Specialty : 12-20-2017 at 10:03 AM.
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  #18  
Old 12-20-2017, 07:15 AM
Bob Kibby Bob Kibby is offline
 
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Location: Arlington, Texas
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Default Similar Power Loss

I posted this several months ago relative to a similar power loss:


Part of my power loss was attributed to sticking carburetor pistons. As I understand it, the pistons move to control carburetor inlet air as the diaphragm moves in response to air pressure changes. The piston motion can be checked by removing the air filter and sticking your finger in the inlet and lifting the piston up and down. The pistons should move freely with very little force. The carburetor air vent lines should end in the same relative location for each carburetor so that each carburetor is sensing the same ambient pressure is another suggestion. Not sure of all the things that can cause sticking pistons but excessive oil on the air filter and bad (old) auto fuel are examples I am aware of. I had EGT differences as high as 200 degrees and reduced power (4,300 rpm) during my episode.

I sent my carbs to Lockwood for the 200 hr service and haven't had any further problems. I also started adding Stabil to my premium auto fuel since I had the power loss problem.

Bob Kibby N712BK (371hrs)
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  #19  
Old 12-20-2017, 01:05 PM
XPPilot XPPilot is offline
 
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Default In flight Rotax power loss

Bob,

Excellent point! Make sure that those short tubes are not exposed to slip stream at all and generating suction to carb altitude balancing. I experienced that during the maiden flight, unfortunately. I let tower to know that I have some engine problems. They cleared me to land any of the 4 runways or grass as long I land safe. I made back to airport. Solved problem by replacing extended hoses by original tubes.

Hope this is on the Lessons Learned list.

Last edited by XPPilot : 12-20-2017 at 04:31 PM.
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