SonexBuilders.net

Hello all.
Wanted to say hi and also ask for your insight on the jabiru engine. I recently purchased a sonex with the jabiru 2200. The aircraft is built beautifully in 2003 and has 560 hrs on it. Yesterday, I was taking it for my first solo flight and a power loss on departure leading me back for a emergency return back to the field.
I started to loose power around 300-400 AGL where the engine would loose power and then suddenly comeback and loose it again. Where I needed to. Constantly work the throttle back and forth whenever the engine lost power to get it back up again.
Looking on the jabiru forums I noticed that this has happened before but no rectification or further posts were posted for the findings so I was hoping someone would have some insight to what might be going on.
After talking to a couple of people they are kind of thinking that it maybe related to a plugged fuel vent line. A good possibility but I wanted to see if anyone else has seen this before and what else I should be looking for or at.
I should mention that Prior to the purchase we flew it with for about an hour and it ran great with no issues. So any help would greatly be appreciated..

Thank you.

Hi wood,
Confirm is the carb the bing or the red aerocarb or rotec?


michael.

WaiexN143NM wrote:Hi wood,
Confirm is the carb the bing or the red aerocarb or rotec?


michael.

Hi Micheal.
Sorry forgot to put that in. It’s the red aero conversion carb.


Mark

This is probably a long shot, but check the finger filter in the fuel tank for contamination. A friend of mine had a Sonex with Jabiru 3300 with aero-carb he purchased from a previous builder. After a couple of hundred hours, he experienced the same symptoms as you are. It turns out that someone had tried to fix a leak in the fuel tank by using a sealer meant for a metal tank, not a fiberglass tank. After a while, this sealer started breaking away from the tank and clogging the finger filter.
Bob Sonex 550

bnvoss wrote:This is probably a long shot, but check the finger filter in the fuel tank for contamination. A friend of mine had a Sonex with Jabiru 3300 with aero-carb he purchased from a previous builder. After a couple of hundred hours, he experienced the same symptoms as you are. It turns out that someone had tried to fix a leak in the fuel tank by using a sealer meant for a metal tank, not a fiberglass tank. After a while, this sealer started breaking away from the tank and clogging the finger filter.
Bob Sonex 550

Hi Bob. Thanks for the reply. I’ll look at that as well.

Mark

Another thought which can happen is the fuel vaporizing on a warm day after being previously run and sat out in the hot sun.
I’m sure there’s a thread here on the “burp tube” to alleviate that problem. If the vapor lock is the problem, park into the wind and open up your oil access door to get the hot air off the engine


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caveman371 wrote:Another thought which can happen is the fuel vaporizing on a warm day after being previously run and sat out in the hot sun.
I’m sure there’s a thread here on the “burp tube” to alleviate that problem. If the vapor lock is the problem, park into the wind and open up your oil access door to get the hot air off the engine


Sent from my iPhone using Tapatalk

Haven’t thought of that but a possibility as the temperatures have been extremely hot here this summer. Thanks for posting

Mark

Hi all.
Finally was able to head out and trouble shoot the problem from the power loss on departure a few days earlier.
Just a recap from the inspection after the power loss on August 17, 2021.
During that inspection it was noticed that there was oil blow by. Nothing to extreme as I most likely filled it a little to much prior to the flight which resulted in a little blow by.
We wiped the engine and cowling down at that point so that was on my list to see if there was an oil leak somewhere.
The second thing we noticed is that the right rotor cap was not as tight and secure as the left one so that was another thing on my list for today.
I also swung the prop through a few cycles to see if any cylinder was noticeably weaker then the others.
August 22, 2021 troubleshooting
OAT 15 degrees Celsius.
Removing the cowlings, the first thing I wanted to tackle was the right distributor cap which had a little play in it compared to the left one.
I removed it and found about a 1/4 Oz of oily water inside. The water could have been from heavy rainfall the last few days blowing into the cowling. But why the oily base. I then cleaned and dried the inside of the rotor cap and secured it properly where there was no play.
The second concern I had was a possible fuel vent blockage hinted by numerous people and posts. So thanks for this. So tested both upper and lower fuel vents and found no blockage.
At his point I started the engine and let it run for about five minutes just at idle RPM around 900 to 1000rpm. Upon shut down I rechecked the the engine for any oil leaks which none were found.

Full power run up next. Moving the airplane into a more secure location and securing it to the backend of my truck.
We then proceed to do a complete full power run up.

Run up #1
Full power to 2650 and decreased to 2620. Throttle increased steadily to full power held for a few seconds then retarded to 900 RPM

Run up #2
Throttle advanced to steadily to full throttle and resulted in same RPM. 2650 decrease to 2630.
Retarded throttle back to 900 -1000 RPM.

Run up #3
Throttle advance steadily to full throttle and held for 30-40 seconds. Giving 2650 RPM increasing to 2680 RPM.
Retarded throttle back to idle to cool down and shutdown.
After shutdown inspected the engine again for any oil leaks or any thing out of the ordinary. Nothing found.

30 minutes later another run up was completed with same steps to confirm readings on first set.
All reading were confirmed with the RPM consistently at 2650 to 2690.
OP: 42 psi
OT: 108
CHT from 295 increasing to 325 longer check. Decreasing CHT with throttle back to IDLE around 1200 RPM to cool.

Not sure if others who have the same engine and aerocarb get the same results so please if you could post what numbers you get as well so I can compare,

Thanks
Wood

pull the plugs and look at condition. I am suspect of fuel in some way since the throttle is what was helping the problem. Although there may be more than one issue. The distributer probably has oil from the distributer gasket leaking. That and the water is enough to make it act up but if you have one good one it should not have given you so much of a power issue. I would look at both distributers, check plugs for fouling and pull off carb and clean it and go from there. An intake leak could make it act up but it would have to be pretty severe to cause that kind of issue. I know the oh crap factor was going on but did you happen to see what your gauges were doing at the time?
Mark

Hi Wood,
I used to have significant fuel vaporization burps/burbles/reduced RPM as well with my Waiex/Jab3300. I also had the Aerocarb. I finally tracked it down to using the first generation Flowscan fuel flow transducer with my MGL EFIS. It was circa 2010 when I purchased this equipment. It has a oriface restriction in it of about 1/8". I had AN6 fuel line installed, and no fuel pump per plans. On hot days (even moderately hot), or situations where the engine would heat soak the burping happened. I ended up just reinstalling the original Bing carby and the Jab mechanical fuel pump that came with the engine from the factory - and the problem went away completely (at no additional cost to me).
Lorin