loosing fuel flow with altitude

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  • #85178

    we’ve spent a lot of time adjusting my 74 414 to get more fuel into both engines during the climb. when I purchased the plane, I noticed about 25-26GPH on climb, and the engines were getting warm as I reached altitude.

    Now we can get them up to 30GPH per side, but as I gain altitude the left engine’s fuel flow drops (with mixture levers full forward). By the time I hit 15K feet it’s down to 24GPH and falling. Any ideas on what could be causing this. My mechanic is recommending I take the 414 to a shop that specializes in fuel systems.

    Brian

    #105881

    Turn the boost pumps on high. That’ll get you another 3-4 gph.

    #105882

    I had the same thing on my right engine.. turned out to be the fuel regulator was bad.. put a new on in and adjusted the fuel flow according to the SID and it’s good.

    #105883

    boost pumps on high work great, I get more than enough fuel flow and can pull the mixture lever back to get the desired fuel flow.

    The only problem with that is that you get a nasty surprise when you switch to the aux tanks and that engine goes way lean.

    will check into the fuel flow regulator, I was guessing there’s something limiting the fuel.

    #105884

    Kelly,
    Did you have any other symptoms of the failed regulator? the other thing I notice is that during cruising, sometimes that side will randomly drop fuel flow by 1-2gph. I can fix it by moving the lever forward, but it only happens on that side.

    #105896

    Yep just like that.. 1-2gph and would end up sometimes with a big split depending on altitude. was getting worse every time I flew it. We tweaked high end 2 times.

    The other thing we found was the fuel pressure was also off and needed set back to the standards required for RAM.

    #105901
    rwelsh
    Participant
      quote :

      Now we can get them up to 30GPH per side, but as I gain altitude the left engine’s fuel flow drops (with mixture levers full forward). By the time I hit 15K feet it’s down to 24GPH and falling. Any ideas on what could be causing this. My mechanic is recommending I take the 414 to a shop that specializes in fuel systems.

      Brian

      It is quite easy to screw in the fuel pressure regulator and see how that works. I would loosen the jam nut and do 2 turns clockwise. If that doesn’t help, then you can return it to the original spot and try something else, but I am at a loss on what else to do short of a total fuel system adjustment. But trying to find a shop with the required gauges and tees and expertise may not be easy..

      #106737

      problem fixed.

      First replaced the FPR. Improved stability of the system. Before when i was leaning for LOP, I had a hard time because temps were all over the place and the engine would surge some. But at altitude, I was still loosing fuel flow.

      Upon further inspection, found a break in the air hose from the turbo to the upper deck of the fuel system. This provides pressure for altitude operations.

      after that fix, it’s running perfect. I think both the FPR and air hose needed to be replaced.

      now that the left engine is perfect, I think I am going to replace the FPR on the right engine because it’s still a little inconsistent at LOP. I find that the EGT temps can surge up and down 30 degrees at higher altitudes while the left side is now completely solid.

      Brian

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