I have a head scratcher type puzzle. On climb out my 350i occasionally has an unscheduled power drop of around a hundred rpm. Not every time, just occasionally. In static tests on the ground it is a brief drop then climbs back up. Like in flight, not every time. Static rpm is around 2600 to 2650 at current prop pitch.

Ideas on how to troubleshoot? Checked gasolators, they were clean. Small leak on hose fitting, turned out to be on a return line, not likely source of air in lines. Fuel pressure is around 48+-.5 psi at full throttle. Pumps run either or, pump 1 or pump 2 runs, never both at same time. Might happen only with pump 1, or it could be coincidental. Seems to be more of an issue on first take-off of the day. Or it might be that I just quit flying when the engine is not running to expectations.

Something temperature related? If so, what?

Engine has been flying for 300 hours since I last did any significant changes/work on it. 650 hours over all. Burning a small amount of oil, leaking a very small amount onto engine mount and fire wall from mystery source.

Ideas? Suggestion’s on how to troubleshoot? Ray did not have an immediate answer. Not something he has come across.


N750RP Cruzer 

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Glad you solved the issue...good info for UL owners Ralph.  Did you happen to notice "before" and "after" fuel pressures values.  You should be able to upload the .cvs files from the Dynon user data log into Savvy Analysis online and review the values.

As to solving the issue…maybe. With a couple of hours of good performance I was feeling positive until I Aborted a takeoff the other night due to slight power bump. Have not had much time to work on it since. The one static test I ran elicited one 70 rpm power drop and slight fuel psi drop from 49.5 to 48 and back-up again. I have already purchased another fuel filter. It will be interesting to see if changing filter again gives me another reprieve. I will install the new software driver so that I can download the data from the Dynon, somehow. 



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