3

33sn

I'm New Here
First flight in recently purchased half of RV12. Partner on extended trip. Last fuel was 5 gals of 93 non-ethanol I put in to fill. previous was hi test ethanol Mogas by partner. Not sure when partner last flew.
Took too much ground to get airborne. Climbed reluctantly, just enough at first to get about 50'. D180 alarm and red ribbon said excessive fuel pressure. Looking for a place to put it down, at full throttle it was running rough, but improved somewhat. I got back to the runway. I am assuming the likely culprit is the ethanol Mogas turning to gel from sitting. Suggestions? Partner/co-builder won't be back for several months. I plan to drain the tank and check the carb bowls for contamination. Appreciate any thoughts, besides lectures. With 2 on board we would not have kept it out of the trees. I see comments about new fuel pump, which As new this I know nothing about.
 
If the gas is old then toss it, but I doubt this is the real offender, but possible if the fuel is real old and left to dry in the bowls. What was the excessive pressure or doesn't that display? You're right to pull the carbs and clean them plus inspect the bowls. It could be the floats are sticking, the needle valve sticking or failing or you actual have debris in the carbs. Until you inspect them anything else at this point is speculation. The ethanol won't turn to gel, but old fuel left in the carb bowls and left to dry can cause some blockage at times.
Once the carbs have been cleaned try a static run up and while you are doing that check the rpm.

The fuel pump could be an offender, but not as likely as many think. No way to check this without putting a mechanical gauge inline if you don't have one on your panel.
What was your take off roll rpm? If it was low you would have been better staying on the ground and shutting down.
 
I suggest that the D-180 log file be saved to a computer for analysis. The data could even be uploaded to docs.google.com or similar website and shared with others. It would be interesting to see what the fuel flow and fuel pressure and RPM were.
An obstruction in the return line could make the pressure go up. Excessive fuel pressure could make the mixture too rich. I am not saying that is what happened, just a possibility.
This is the first report that I remember reading about where high fuel pressure caused a loss of power. Usually high fuel flow is the complaint.
Joe Gores
 
Check the fuel pressure set point. At least you'll know the lower limit on how high it got. Mine runs about 3.6 psi in normal ops.
 
To clarify, I was referring to the alarm set point. The 3.6 psi refers to my normal fuel pressure rating.
 
The max pressure now is 7.2 psi. If you had it at the old 5.8 then you may need to adjust the alarm yellow and red limits in the menu.
 
There are some ROTAX SBs about deteriorating fuel line replacement for certain serial numbers. Check for compliance with those since you bought the plane used.

There is inconsistency about whether or not you can get a replacement newer type fuel pump for almost "free." I did. Call Lockwood. It is an easy replacement, ROTAX-Owner has a video. I paid for a new pump and got a refund when I sent in the old. New pump has a 3rd tubing fitting for a drain line pointing directly down.
 
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