Orientation of ROTAX Fuel Pump

Discussion in '2-Stroke Aircaft Engines' started by Tuneturkey, Dec 3, 2019.

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  1. Dec 3, 2019 #1

    Tuneturkey

    Tuneturkey

    Tuneturkey

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    Just mounted the ROTAX diaphram fuel pump in the horizontal position with the impulse line out the bottom. While watching an EAA video, a review of an installation pointed out that the fuel pump was improperly mounted, in the vertical position. I also have been told that the impulse line must not be longer then 11 inches. Can anyone point me to a reference where mounting the fuel pump is discussed?
    Thanks
     
  2. Dec 3, 2019 #2

    Dana

    Dana

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    The impulse line should definitely be kept as short as possible... and also use the proper heavy wall pulse line, not ordinary fuel tubing.

    I believe the Rotax rectangular pumps have a weep hole on the same side as the pulse line, this should be pointed down to let any oil drain out. I'm not sure about the round pumps. The Mikuni pump, which I used on my Kolb, is identical to the Rotax pump but without the drain hole. Having the line down from the pump also lets any oil drain to the bottom of the loop and be visible (I never saw any in mine).
     
  3. Dec 4, 2019 #3

    wanttobuild

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    Tuneturkey

    You are dealing with a very important part of the two stroke engine installation. CPS has some good info on their site. Also see the Air Creation Trike fuel system installation. My trike had a short pulse line, the red stuff, going to a horizontal fuel pump. I rebuilt mine, but easier to buy a new one. Don't guess about your fuel system, if unsure ask questions. It has to be bullet proof. I also used a shutoff valve for the primer line, after priming shut off the fuel source.
    What are you installing your pump on?
     
  4. Dec 4, 2019 #4

    Tuneturkey

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    Wanttobuild,
    Installing on a 503UL. I did see some oil in the pulse line, confirming a comment from Dana. Don't know if oil in the line is a problem or not, but a few drops are visible at the low point in the line (can't see in this pic). I had the pump higher up on the firewall level with the top of the fuel tank, and following a comment, moved it down to the location in the pic. Could shorten the line 2-3" by rerouting behind the carbs, for a new length around 12-13".
    Thanks for the input!
    IMG_3571.JPG
     
  5. Dec 4, 2019 #5

    wanttobuild

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    You need the red colored pulse line,thick wall stuff
     
  6. Dec 6, 2019 #6

    Richard6

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    I've been biting my tongue on this, but I feel that I must say this.

    These engines will put some oil into the pulse port. Without proper management of the pulse line, the oil can collect in a low spot on the line a limit or completely stop the pump from working.

    IMHO the pump should be above, i.e. higher than the pulse port and the pules line should be as short as possible using heavy walled tubing and not have any low spots in the line were oil could collect.

    This way, any oil that gets into the line will drain back into the engine as it is running.

    I had an issue with the fuel pump on my SCCA F500 car that used the Rotax 500CC engine. I originally had the pump low in the frame with the pulse line going up to the pulse port. After about 20 mins on track the engine would start to sputter and run rough. After several sessions, finally figured out that the oil will puddling in the line pump causing poor operation of the pump.

    Moved the pump up above the pulse port and made sure that there was no low spot in the routing. Worked great after that.

    Richard
     
    proppastie and delta like this.
  7. Dec 7, 2019 #7

    proppastie

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    seem like we have lots more members than posters.....please share.
     
  8. Dec 7, 2019 #8

    Tuneturkey

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    Thanks for the input Richard!
     
  9. Dec 12, 2019 #9

    wanttobuild

    wanttobuild

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    2 stroke engines are lightweight and produce a lot of power.
    Thank you Richard for contributing, as shared knowledge help to make a safe installation.
     

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