912iS - Erratic Fuel Pressure after Stator SB Work

[andyb]

I recently had the 912iS service bulletin performed to replace the stator, and the work was done by a very experienced, professional Rotax shop.  This entailed removing and re-installing the engine.

 

On the 2 1/2 hour flight home, I had a low fuel pressure warning about 1/2 hour into the flight.  It initially went to about 39 psi, and at one point went to 16 psi.  Throughout that time, the engine ran normally, and fuel flow never changed.  After the dip to 16, it returned to normal for the duration of the trip.  One anomaly I did notice was that when I put on the aux pump, the pressure went down, but still at the low end of the green range.

 

After returning home, I spoke with the person at the shop, and we both agreed that the problem was probably an air bubble in the "detour" the fuel line takes to the sensor.  On the ground, I independently checked both pumps, and they both ran normally with normal fuel flow pressures individually and together.  The anomaly with the pressure going down with the aux pump on went away, i.e. the pressure went up a bit with the aux pump on.

 

Yesterday, another pilot and I flew the plane.  All was normal until about 10 minutes into the flight, at which time the pressure went way up, well into the red zone above normal.  I pulled the power back a bit, and the pressure went down, this time in the red zone below normal..  It went to about 29 psi.  We returned back to the airport and landed normally.  Throughout the time, the fuel flow was normal.

 

Complicating things is that my home field has a number of good FBO's, but no one in the area that's expert on Rotax engines.  Closest one is a 1 1/2 hour flight away.

 

Thoughts?

 

Thanks,

Andy

[Roger Lee]

It could be air, but it is very likely a bad connection.