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Thread: Intermittent primer (O-470L C182B)

  1. #1

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    Intermittent primer (O-470L C182B)

    I've had 3 A&P's look at the primer and it still doesn't work. They looked over everything. We used an overhaul kit to replace the o-rings. It is still doing the following:

    Sometimes it works normally on a cold start. It almost always works normally on a hot start.

    Most of the time (usually after the airplane hasn't flown for 7+ days), the primer doesn't work. It pulls out and pushes back into the panel with no resistance and no sound. If you pull it out when it's not working this way, it will slowly be sucked back into the panel. It doesn't move any fuel. Sometimes if you physically hold the primer knob back in the aft position for 20-30 seconds, then push it in and prime again, it will start working. This doesn't always work either. I don't know what to do. Should we try to replace the knob/control?

    Thanks!

  2. #2
    stewartb's Avatar
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    Spin the knob a little and then pull the primer out VERY slowly to start some fuel flowing. If that fails rotate the knob a bit and try it again. Dry primers after a few days are common. You just need to figure out how to get yours to pull a drop or two, then you're home free.
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  3. #3

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    Ok, thanks Stewart! Sure enough I did try it just now and it would only work with the "notch" rotated toward the ground "6 oclock". Got 10 dry pumps with the notch pointed up and to 9 oclock.

  4. #4

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    I've had this happen on a good number of primers, likely the check valve ball sticking. It won't unseat and let fuel in to fill the chamber and sucks the plunger back in some. No magic trick, I just open it up and give it some Kroil and try to blow shop air inward from the inlet fuel port. Take it out of the plane first, bad stuff happens when shop air meets installed equipment, especially if it is a pitot line.

    A&P school lesson;
    -instructor "clear the pitot line"
    -teammate "I got this", airspeed glass lands on seat of Champ then "I'm gonna fess up"
    -other teammates "look , a new airspeed just sitting over there"
    -instructor "gather round gents, this is a teaching moment. Now show me how this happened" More glass on seat of champ.
    -entire team, broken up and remaining members dispersed to other class teams.

    Ken
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  5. #5
    gntw's Avatar
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    Need to put fuel lube on O rings very little then install plunger. Aircraft spruce has it .1 tube will last u a life time. Good on fuel valves to
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  6. #6
    stewartb's Avatar
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    Fuel Lube is long gone. If you’re looking to buy a tube look for EZ Turn.
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  7. #7

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    Don’t forget to check your primer line nuts at the cylinders while you are going through the system. They are often cracked from overzealous installation.

    Quote Originally Posted by Narwhal View Post
    I've had 3 A&P's look at the primer and it still doesn't work. They looked over everything. We used an overhaul kit to replace the o-rings. It is still doing the following:

    Sometimes it works normally on a cold start. It almost always works normally on a hot start.

    Most of the time (usually after the airplane hasn't flown for 7+ days), the primer doesn't work. It pulls out and pushes back into the panel with no resistance and no sound. If you pull it out when it's not working this way, it will slowly be sucked back into the panel. It doesn't move any fuel. Sometimes if you physically hold the primer knob back in the aft position for 20-30 seconds, then push it in and prime again, it will start working. This doesn't always work either. I don't know what to do. Should we try to replace the knob/control?

    Thanks!
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  8. #8

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    Quote Originally Posted by JohnnyR View Post
    Don’t forget to check your primer line nuts at the cylinders while you are going through the system. They are often cracked from overzealous installation.
    and pull the primer nozzles, you will be surprised how many get clogged.

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