IO-470D Fuel Pump/Servo problems

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    We have owned our new to us C-310F for 6 weeks but only flew it for 3 days until we realized the aircraft needed an entire FWF overhaul on both engines (all new fuel and oil hoses, overhauled fuel pumps/servos/flow dividers, new air/oil seperators, new spark plugs wiring harnesses, new spider lines with clamps, mags overhauled, we didn’t touch the alternators or starters). The left engine fuel line was dated April 1960!

    After all this, the left engine finally checked out. The right engine however, has a mag drop of over 500 rpm due to an overload of fuel to the cylinders. So we sent the servo and the pump back to Kelly aerospace in AL. Again to be overhauled again.

    QUESTION: if this doesn’t solve the problem, can you suggest other vendors where these ancient parts can be properly overhauled, tested and returned so that they’ll function as they should.

    We’re nearing the finish line, but may need some advice to get the ball into the end zone.

    Hopefully we can get this airplane back in the air soon, she is due for a new pilots panel (Aspen 1500 dual PFD/MFD, STEC-50 autopilot and a JPI 760, upgrade Garmin GTX330 to an ES, and a new oxygen bottle) next month, but I’ll save that for another day.



      You don’t suppose the boost pump is on; either purposely or it is miswired?


        I only use Mike’s Fuel in Tulsa. Great family and he is willing to answer questions.

        quote RWELSH:

        I only use Mike’s Fuel in Tulsa. Great family and he is willing to answer questions.

        I 2nd the rec for Mike’s Fuel Metering. Really great to work with and prices are reasonable.

        Can you describe the mag drop you are seeing? I am not sure I understand the 500 rpm part.


        Thanks for the recommendations, I just talked with another vendor, Aircraft Accessories, also in Tulsa and discovered a few interesting items. I will also consider using the other shop in Tulsa if needed in the future.

        First, Aircraft Accessories said that my overhaul shop probably uses after market parts, AA only uses OEM parts when overhauling items (in this case fuel pumps/throttle bodies). My contact also said that the O rings in the pumps are very sensitive if they are not installed correctly, and they can be blown out on the first application of pressure, causing a too rich fuel condition (exactly the problem I’m having). He also said that these older engines need a longer throttle link rod when reinstalled so that the throttle body can cover the entire range of fuel metering. A throttle linkage that is too short would make the mixture too rich (again, my exact problem).

        The magneto drop we were seeing was during the engine run up after reinstallation of the fuel components (the last part of the FWF overhaul we accomplished). During the single mag check on the right engine the mechanic was getting over 500 RPM mag drop on a single mag, due to too much fuel being metered to the cylinders. The left engine checks out fine.

        The plan now is to reinstall the fuel pump and throttle body again, but call AA in Tulsa to make sure the throttle linkage length is correct prior to running the engine. If it fails this time, I’m going to send the parts to AA (after I pull all my hair out for the third time).

        It is important to note that setting up the engine fuel metering system in accordance with the TCM Service Information Directive (SID) 97-3C is a must to ensure all the fuel pressures are correct. I’m guessing that this has not happened on my airplane for probably many, many years, but glad to know that it’ll be done correctly when finished. My personal thanks to the TTCF website for having all this information available, I have learned more about Continental fuel systems that I would’ve ever thought possible.

        Hopefully this information will prove useful to someone else, so you don’t have to go through the frustration I have for the last 4 weeks.


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