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Fuel Pressure Issue

Took off with full tanks - after a decent from 8500 to 4500 / 1.75 hrs into the flight - low fuel pressure alarm comes on and pressure is at 1.8psi

I landed at the nearest airport and talked to my mechanic who recommended topping off the tanks. After doing that, the run-up showed normal psi, flew 2 rounds in the pattern and psi remained 4.5 - 5.0. I continued to my destination - .5 hrs - without any problems.

Two days later, on our flight back home, we had no problems until we were once again 30 min from our destination and after descending from cruise altitude. Fuel pressure once again dropped down to 1.8psi. We landed...topped off, flew a round in the pattern and everything was back to normal.

Needless to say, it was a trip from **** and now I am trying to figure what the problem is.

100LL only - no Mogas
 
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I assume an RV12?
You have to verify the fuel pressure readings. Is it real, or a sendor anomaly?
Plumb in a KNOWN good mechanical guage and check the readings. Probably going to be the same, since you didnt say of any other issues.
Yes, a Rotax 912ULS will run on a low fuel pressure, especially in decent with the throttle pulled back.
But, I'd consult with the Rotax experts.
Tom
 
Venting problem ?

I never been near an RV12 but Losing pressure during descent has me wondering about fuel tank venting problem. A slow or partial blocked vent that equalizes pressure over time.
 
I experienced something similar & transient a few years back with my RV-12 as well. Lower fuel pressure readings (mostly in the yellow) when descending from altitude (>5,000) and usually on a longer cross country trip. 100LL or various brands of mogas, didn't make a difference. After replacing the 912 engine driven pump at 5 years and the Facet pump at the same time, this issue went completely away. Could be circumstantial, but I suspect my engine pump was failing and this was aggravated somehow when descending from altitude.
 
Had exact same thing happen to me, go to Vans site and look at this, N 18-07-12 Notification
That fixed it for me,never had it come back again.
 
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