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High fuel pressure with new Corona pump

in General Tech Discussion 11 years ago
Hi flying birds,
I do have replaced my 500 hrs fuel pump with the new recommended Corona... I used to have a pressure arround 2.2 PSI and now it raised above 4 up to 4.5 PSI.... Is it not to high? Could it not make the Bings leaking fuel? Thanks for your answers and enjoy the beauty of the earth from the sky.

  • Re: High fuel pressure with new Corona pump

    by » 11 years ago

    The pressure limit with the Corona pump is 7.5PSI so you should be fine with 4.5PSI.

    The Rotax Two stroke engines which also have bing carbs (with virtually identical float level control) have always had a 7.5PSI Bar upper limit and have been OK.
    Thank you said by: Jean-Paul Koeune
      
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  • Re: High fuel pressure with new Corona pump

    by » 11 years ago

    4.5 psi is normal with the newer corona pumps. Some maybe slightly lower and some slightly higher and many times this is the difference from plane to plane pressure sending units. You wouldn't believe how many sending units are off by 1-3 psi. Many who never had a re-circulation fuel line will need to install them. This is absolutely not the same pump as the older Pierberg or AC pump. Don't fight it you will need a re-circulation line and it should be easy to install. Some of these pumps do run higher pressures and those that have never had a carb rebuild and have old carbs may need to do so to freshen up the needle valve in the carbs to keep a marginal carb from leaking past the needle valve and it is just as important when you do rebuild to make sure your float height is correct by measuring the float arm height and do it on both sides of the float arms for each carb. When turning on an electric backup pump it should only raise the pressure by .5 psi or slightly more. Remember when installing the re-circulation line that the restrictor is a #35 Mikuni slow jet or idle jet. It is not the same as a .35mm.
    Bing jets work on orifice size and Mikuni jets work on flow through the orifice. Two different things. People who have had high pressure problems, leaking carbs and rough running engines usually had no re-circulation line or a bad pressure sender. Early on there were some high pressure pumps, but that should mostly have been corrected.
    Re-circulation lines also help control any vapor lock, but not everyone has a problem with this depending on your specific engine setup and aircraft design. If you have a digital fuel pressure display with an alarm set for the older 5.8 psi max you will need to go into the menu and set the new max fuel pressure limit.


    Special consideration: If you do experience high pressure or too much fuel flow a slightly larger Mikuni idle jet for the re-circulation line could be used, but be very careful and do it with some testing and forethought. I say this with some reservation, just don't blunder through it.


    Just to give you some perspective on a re-circulation line's importance. The new 912is engine may use (depending on your personal cruise rpm) around 20 lph, but the system circulates 114 lph.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Jean-Paul Koeune, YEN NIEN YU
      
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  • Re: High fuel pressure with new Corona pump

    by » 11 years ago

    Roger:

    I've got a 912UL on a RANS S-12S (Pusher). Had carbs rebuilt by Lockwood. Only a couple hours on carbs. Installed a new type mech fuel pump from Lockwood. I have Dynon Skyview system with Dynon sender for fuel pressure mounted to Rotax fuel block. Fuel distr block has return line with stock restrictor needle. Return line is to supply side of pump as return to tanks not possible.

    My typical scenario is at startup and warm-up to run 4.8-5.2 psi. Once I warmup to operating temps I am typically at 5.5-6.5 psi.

    Is this normal/satisfactory, or do I have an issue?

    Thanks,
    Corey in Tampa.
      
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  • Re: High fuel pressure with new Corona pump

    by » 11 years ago

    Hi Corey,

    The pressure numbers are well within the new pump specs so I wouldn't worry and after a little time they may settle a little further. The fuel supply line side of the fuel re-circulation line is okay, but I hope it was put a ways upstream. Placing it right up by the pump isn't a good placement. Many have plumbed it back to the gascolator, wings or header tanks.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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