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What is the best way to ck if main fuel pump is bad when shuting down turned off aux pump engine shut off ?

 

  • Re: fuel pump

    by » 9 months ago


    I’m not sure I fully understand your question, but since the fuel pumps deenergize when the engine shuts down, to verify both are still working at the end of a flight, before turning off the Lane circuits, I always watch the fuel pressure as I shut off one of the pumps.  If the engine keeps running, I know the pump that’s still on works, and if the fuel pressure drops slightly, I know the one that was shut off was working. 

    After the Rotax fuel pump SBs and the HIC module issues with the Van’s RV-12iS, it’s on my shut-down checklist. 


  • Re: fuel pump

    by » 9 months ago


    If you were running both pumps during the flight, and then before shutdown you turned off the aux pump and the engine stopped, then the main pump was definitely not running at the time.  It may be completely failed or intermittently not working, but either way it needs investigation. 

    This brings up the question of rather or not to run both pumps during the entire duration of a flight.  Some do because they like having the redundancy online. I however don’t because with two pumps running you won’t know that one has failed until the next flight when you do the preflight checks.  I would rather risk having to do an inflight restart than not know one pump has failed. I do as Rotax recommends, which is use two pumps for takeoff and landing, and run on the main pump the rest of the time.   


  • Re: fuel pump

    by » 9 months ago


    Hi Jeff

    I am in the camp that you run them both in flight, not just take off and landing.  In a fuel injected engine if you are running one pump only and it stops the engine instantly stops.  it is easy to know if you have a failed pump at the end of the day, simply carry out the same check you did in the beginning and turn one off, turn it back on and cycle the next one.  You then shut down the Lane A and Lane B and switch off both pumps.  

    Naturally if you are going to fly on one pump be sure to activate the other before you start your descent and get into approach.  We might need that altitude to get a restart if you have a problem.  The pumps are good to go to TBO so I don't believe that should be a concern.  Rotax is constantly working towards finding a better supply of fuel pumps and they have improved a lot since 2021. 

    if you have been following the type 916 they have a completely new supplier for that engine (fuel demand is a lot more) You will no longer have the stainless box on the pumps, they will be compliant with the fire standards without it.  

    Cheers


    Thank you said by: Jeff Blakeslee

  • Re: fuel pump

    by » 9 months ago


    I was flying after landing I shut off aux pump engine stopped. I the would like to ck main pump to make sure it is bad on not a electric problem. Not sure how.


  • Re: fuel pump

    by » 9 months ago


    Ronald,

    Turn on the Start Power switch, and then check that both the aux and main pumps run independently and together.  If the main pump does not run, check fuses F4 and F5 in the Rotax fuse box. I say check both fuses because the main pump usually connects to F5 and the aux pump to F4, but it could be reversed.  If a fuse is blown (probably F5) you likely have a bad main pump. In this case, don’t just replace the fuse, have the pump inspected and run on a test bench.  

    If no fuses are blown, swap the wire connectors at the pump then try running each pump again.  If the problem changes from the main to the aux pump, the problem is in the wiring circuit.  If it stays with the main pump, the pump is bad.  Remember that once you swap the connectors the aux pump switch operates the main pump.  


    Thank you said by: Rotax Wizard

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