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Just had my annual done.  Had minor  fuel leaks in both wings.  These were repaired,   Fuel filter was replaced at 180 hours, now at about 320 hours, so not due until about 380.  Flight home of about 30 minutes was uneventful.  I had fuel down to about 10 gallons and today was going to fly to a place about 15 minutes away where fuel is about 50 cents less than home field.  I use only 100LL as Mogas not readily available near me and I don’t trust it.  On way, I noticed fuel pressure steadily increasing from normal of 45/46 to about 49.  Decided to return home.  Fuel pressure steadily increased and on short final pressure was in the red at 55.  Called A&P and he and I agreed we should replace fuel filter before next flight.  Any other thoughts on this?  Does pressure increase when below 10 gallons?  Normally I fill it up below 20, but had it low so A&P could more easily pull the wings.  Thanks.

  • Re: Fuel pressure rise

    by » 6 weeks ago


    hello Mac

    First thing is the fuel filter, could be contaminated.  This indeed will cause high fuel pressure.  If it is contamination consider cleaning the fuel pressure regulator also.  You did not say if this when running on both pumps or just one.  The issue is still the same however, check for contamination.  

    I doubt that the full or empty state of the tanks has much to do with this.

    Cheers

     


  • Re: Fuel pressure rise

    by » 6 weeks ago


    Mac,

    If your fuel pressure sender is before the fine filter than a partially clogged filter would raise the fuel pressure.  But the rate of rise seems too fast for a filter loading problem unless you got a bunch of dirty fuel that made it past the coarse filter.  Other possible problems include:

    - A defective fuel pressure sender

    - A defective (Rotax) fuel pressure regulator

    - A problem with the fuel return line, which likely runs through the (double) fuel selector valve.  It would be interesting to know if the problem goes away when you switch tanks, since that also changes the fuel return path respectively. 

    I'm troubled by the fact that this happened right after "fuel leaks in both wings" were repaired. Do you know precisely what was done?  


  • Re: Fuel pressure rise

    by » 6 weeks ago


    Just thinking....perhaps sealant from the repair has made it from the tank to the filter.  For sure check the internal part of the regulator while you are at it.  

    Cheers


  • Re: Fuel pressure rise

    by » 6 weeks ago


    Where is the coarse filter located?  This is a 2019 Flight Design Super Sport i.  I see that filter referenced here, but don’t know where to find it.  


  • Re: Fuel pressure rise

    by » 6 weeks ago


    I was only using the primary pump.  Normally turn on auxiliary when landing, but didn’t want it to go higher.


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