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Thread: Draining Old Gas?

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    Draining Old Gas?

    The Haynes manual I have says the fuel pressure regulator is with the fuel pump on the rear bulkhead yet someone I thought was pretty sharp pointed out what sure looks like a regulator under the hood on the passenger side of the engine. I'm told the best way to drain fuel is by a hose on the regulator and using the pump?

    I've also read somewhere that even with cars having overturn valves it's sometimes possible to snake a hose down the filler neck and use a good old gravity siphon. Is this possible on a Miata?

    Probably from a few years driving a gas tanker and hearing every story ever told about bad happenings with gasoline I'm probably a bit paranoid about using anything that may spark around gasoline.

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    Ninja Messiah kung fu jesus's Avatar
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    Draining Old Gas?

    What year?

    Some have a drain plug.

    Otherwise, you can use a transfer pump down the filler next or disconnect the fuel line at the fuel rail and add a jumper on the diagnostic port to let the in-tank pump move it into the container of your choice.

    Out of curiosity, why are you trying to drain the tank?

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    3,000 rpm - starting to feel the power atlex's Avatar
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    You can definitely syphon out the gas.. :-)

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    Admin / Pit Boss / Miataholic Phatmiata's Avatar
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    atlex going the old school route, mmmmmmm yummy. tastes great less filling!!

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    Quote Originally Posted by kung fu jesus View Post
    What year?

    Some have a drain plug.

    Otherwise, you can use a transfer pump down the filler next or disconnect the fuel line at the fuel rail and add a jumper on the diagnostic port to let the in-tank pump move it into the container of your choice.

    Out of curiosity, why are you trying to drain the tank?
    It's a '99. Long story not worth telling but draining the gas because it's old and stanky and the car won't run, been sitting for a while. Haven't tried down the filler neck due to conflicting opinions but Harbor Freight's cheap enough, guess I'll pick up a siphon pump and see how it goes.

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    Quote Originally Posted by Phatmiata View Post
    atlex going the old school route, mmmmmmm yummy. tastes great less filling!!

    And a great opportunity to practice fire breathing!

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    Yeah, the FPR is on the pump hanger bolted to the top of the tank under the parcel shelf covers towards the left (driver side).

    I don’t know how old your current fuel pump is or the mileage, but a nearly empty tank is a great time to replace it, the hanger seal, and the duck foot. About $100-120 in parts and about 30-45 minutes.

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    3,000 rpm - starting to feel the power atlex's Avatar
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    takes a few days to get the taste out of your mouth if you fail to time it right. or don't pre-prime the siphoning hose.

    I recommend just getting one of those 12v fluid transfer pumps.

    I'd advocate against pumping bad gas through your fuel pump and fuel filter. why make those things potentially worse.

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    Quote Originally Posted by atlex View Post
    takes a few days to get the taste out of your mouth if you fail to time it right. or don't pre-prime the siphoning hose.

    I recommend just getting one of those 12v fluid transfer pumps.

    I'd advocate against pumping bad gas through your fuel pump and fuel filter. why make those things potentially worse.

    Good point!

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    Well, siphoning doesn't appear to be an option, the hose only goes down the filler neck a short distance before reaching something blocking it.

    Oh well, back to square one.

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    You can remove the filler neck tube and access the tank directly.

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    Quote Originally Posted by kung fu jesus View Post
    You can remove the filler neck tube and access the tank directly.

    I've been busy with other things and haven't had a chance to eyeball it. Is that removal relatively easy? I'd rather siphon it than pump a bunch of bad gas through the system.

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    Yeah. It’s the big rubber tube in the drivers side tunnel at the back of the trunk.

    Take the side off at the tank.

    Check the condition of the tank nipple while it’s off. It’s not uncommon for some corrosion to start there, giving off a little fuel smell in the trunk from time to time.

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    Burdell (10-04-2021)

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    Quote Originally Posted by kung fu jesus View Post
    Yeah. It’s the big rubber tube in the drivers side tunnel at the back of the trunk.

    Take the side off at the tank.

    Check the condition of the tank nipple while it’s off. It’s not uncommon for some corrosion to start there, giving off a little fuel smell in the trunk from time to time.

    Thanks! I appreciate the input, hopefully I'll get to it soon. As so often happens everything happens at once.

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    Quote Originally Posted by Burdell View Post
    Thanks! I appreciate the input, hopefully I'll get to it soon. As so often happens everything happens at once.

    This may be helpful to illustrate the tube and areas I referred to in the previous post:

    https://mazdaroadster.net/showthread...l=1#post214112

    The filler tube pics are towards the bottom of the post, including a p/n if you happen to run into the same issue. That car is also a '99.

    "That fuel filler hose is part number NC10-42-231 , it's called a Connector Hose on the invoice."

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