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Thread: How to prime fuel system with mechanical fuel pump?

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    Registered User BoldUlysses's Avatar
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    Default How to prime fuel system with mechanical fuel pump?

    Getting ready to start the car in the next week or so. I want to give the engine its best shot to fire up on the first dozen or so cranks. That said, what's the best way to prime the fuel system with my (new) mechanical pump? Can I remove the valve cover and actuate the pump lever by hand until fuel makes its way to the carbs? Or is there a better/easier way?
    Matt | Spannerhead.com | Original Z Owner #129 (2nd Gen) - '72 240Z (HLS30-93069) '95 525i/5 '05 MPV

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    Registered User LeonV's Avatar
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    The better and easier way is to manually fill the carb bowls with fuel and start the car.
    2/74 260Z

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    Registered User BoldUlysses's Avatar
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    Plan to do that, but won't the car just stumble and die until the lines, pump and fuel filter are filled? The objective is to avoid any break in fuel supply.
    Matt | Spannerhead.com | Original Z Owner #129 (2nd Gen) - '72 240Z (HLS30-93069) '95 525i/5 '05 MPV

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    Registered User Gary in NJ's Avatar
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    Gravity.

    - or -

    Suction. You can get a large syringe and draw the fuel through the lines.
    Gary
    Guardian of HLS30-91415
    Previous Owner of a 10/70 240Z ('83-'85)

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    Registered User LeonV's Avatar
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    Quote Originally Posted by BoldUlysses View Post
    Plan to do that, but won't the car just stumble and die until the lines, pump and fuel filter are filled? The objective is to avoid any break in fuel supply.
    Nope. It will idle for an unexpectedly long amount of time on just the bowls. With the engine running, the pump will get the fuel moving very quickly.
    2/74 260Z

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    Registered User BoldUlysses's Avatar
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    Understood. I'll just fill the bowls and call it a day, then. Thanks!

    Now to figure out how to apply the fuel tank sealer without clogging the tank intake screen/sock (if there is one)... Sigh. Onward.
    Matt | Spannerhead.com | Original Z Owner #129 (2nd Gen) - '72 240Z (HLS30-93069) '95 525i/5 '05 MPV

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    Quote Originally Posted by LeonV View Post
    It will idle for an unexpectedly long amount of time on just the bowls.
    I've done this and can vouch for the claim above. I didn't actually time it with a stopwatch or anything, but it was at least thirty seconds of idling, and maybe as much as a minute before the engine started misfiring.

    If you haven't sucked fuel through the pump by then, you've got other issues.

    Oh yeah, and if your idling engine sucks the bowls dry in less than twenty seconds, then you've got other issues as well.

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    Registered User Bonzi Lon's Avatar
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    Quote Originally Posted by BoldUlysses View Post

    Now to figure out how to apply the fuel tank sealer without clogging the tank intake screen/sock (if there is one)... Sigh. Onward.
    Not much to worry about. There is no screen / sock, just open tubes. The pick up tube is about 3/4 inch off of the bottom of the tank, the return is further up. With a mirror on a stick, illumination through the sender hole and looking through the filler hole you can see the tubes over the baffle. When the sealer was curing I made sure and ran compressed air and a thick wire through each tube, just to make sure.

    The longer the cure time on your tank, the better.

    Bonzi Lon
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    POR-15 recommends 4 days before putting fuel in, so I'm going to give it that. Good to know about the lack of a screen/sock as well. I like the thick wire + compressed air trick. How long did you leave the compressed air hooked up?

    Thanks!
    Matt | Spannerhead.com | Original Z Owner #129 (2nd Gen) - '72 240Z (HLS30-93069) '95 525i/5 '05 MPV

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    Registered User Bonzi Lon's Avatar
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    The air was just to make sure the tubes were open along with the wire.

    You might let the tank 'sun cure' when you can.

    Bonzi Lon
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    Registered User BoldUlysses's Avatar
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    Right; but you didn't leave the compressed air hooked up the whole time, did you? I was just thinking about leaving the wires in the whole time, as you suggested, but only blowing compressed air in for the first, say, 6-7 hours or so.
    Matt | Spannerhead.com | Original Z Owner #129 (2nd Gen) - '72 240Z (HLS30-93069) '95 525i/5 '05 MPV

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