Fuel Pressure Fluctuations

Hey Jason,

Sling TSI owner here also with a 915. I had a similar problem with fluctuating fuel pressure but only on my right tank. I have the Aerospace Innovation NaviFlow Fuel manifold and the Fuel Pump Control Module (FPCM). 

Strangely I didnt start getting fuel pressure fluctuation until after I pulled the rubber check valves from the wing root, facet fuel pumps as recommended by Midwest Panel Builders. I tried different fuel and altitudes and it kept just randomly fluctuating but with no perceptible changes with how the engine was running. Additionally both my absolute pressure and normal fuel pressure sensors were showing the fluctuation. I was going to put the check valves back in the facet pumps but now the fuel pressures have stopped fluctuating for about the last 15 flight hours. 

Thank you for the information!  I had the fluctuation before removing the check valves with the boost pumps.  There is a serviceable filter at the boost pump-mine were terribly dirty (picture attached).  Cleaning out the fuel pressure regulator, however, was the only thing that has lessened the fluctuations to near zero.  Fluctuations came back after about 3 hours of flight of doing so the first time.  Right before leaving Midwest, I went from almost a full psi swing in both directions, down to stable after cleaning out the regulator again (which didn't appear dirty), and not at 3 hours of flight yet to see if it comes back.  Although the fluctuation only occurred with the left tank, that was the only "temporary" fix that worked.  It's my hope the fluctuations do not come back.  Happy to hear your fluctuation is currently not present.  

If the problem resurfaces I'll have to try cleaning the fuel pressure regulator. I am not trying to tear into things if I dont have to. How have your manifold temps been? Now that it is cooling off Im not having problems but my manifold temps will exceed limits if im not watching them and climb high 17K or if the ground temp is high 110F. Just wondering your experience as i see not having it displayed on the G3X. I am very regularly in the "extended envelope".

Manifold temps have been within limits; however, the hottest outdoor temps on the ground experienced here are around 90 degrees.  You sound like Arizona weather!  Hard to check without the upper cowling off, but I did have a faulty radiator causing hotter temps earlier in the year.  It got damaged most likely during an oil change on the engine side.  It wasn’t until it fully failed that temps shot up and was thankful to be near an airport.  Something to possibly check.  

Hi all

It is worth to note that the fuel pressure regulator is a mechanical device.  it can overshoot and undershoot by a margin.  (see latest ops manual from Rotax)   The regulator diaphragm can get tired and it is a 5 year time life part also.  The centre slug can be changed, not the whole housing.  I don't know how old yours might be, worth considering I think.  Also be sure to replace your fine filter, it can have an effect on pressures. 

Cheers