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Thread: Fuel Pump Runs, Does Not Pump Fuel...

  1. #1
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    Default Fuel Pump Runs, Does Not Pump Fuel...

    So first off, the 280z from my other post is just fine, I've been driving it daily for however long it's been with no issue

    ...That's when I get cocky and get another car!

    So, the fuel pump was suspect; I wound up getting twelve volts at the terminals when the AFM flap was open, but the fuel pump wouldn't run; new pump, problem solved.

    However, rather than pumping any fuel, it seems only to make noise; i have the fuel line from the pump inserted into a jar for the time being, no dice on getting any fuel.

    I drained the gas tank, the gas inside was liquid rather than solid syrup/rust/bits of fuel tank, just smelled a bit odd (ten years old presumably) so I was fine with re-filling the tank without fear of issue... But I'm going to again check for blockage now.

    So of immediate concern is a notice on the installation guide, something to this effect: "if fuel pump is wired with reversed polarity, pump will run but not pump fuel"...

    Now I checked the terminals with a multimeter to ensure that + met + and - met -... Is it possible though that this new pump is wired reverse of the original? I'm extremely leary of reversing the terminals as I was previously under the impression that this would do nothing but kill the pump.

    So is it possible that the +/- terminals on my new pump run reverse, and if so is it safe to switch them in order to check?

    Thanks,

    -Dan

  2. #2
    Supporting Member EScanlon's Avatar
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    Default

    I think you found your own answer in the installation guide. If it's wired backwards it will run but not pump fuel... which is the situation you have now.

    Reverse the wires and see if that gets it to pump.

    E
    71 240 920 Gold
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  3. #3
    Z geek at large FastWoman's Avatar
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    There's a larger post and a smaller post. At least on my '78, it's impossible to place the smaller wire lug around the larger post. But as you say, maybe the part is incorrectly wired.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

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    This pump has both wide and thick terminals, but there are also connectors present here that can be interchanged between them after the flat terminals.

    So I'm thinking, disconnect the pump to check for fuel tank blockage, and while I'm at it stick a line from the pump to a jug of fuel to see if it won't get sucked up. If not, cross fingers, reverse polarity. Unless someone warns of impending doom

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    No reason to cross fingers. That's why the instructions don't say "pump will be destroyed!" just "fuel will not flow". I would switch the wires first while you have the gasoline all sealed up. Less chance of a gas fumes meeting sparks. Plus it's easy and quick and will answer one question.

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    ...Well, that sure worked I've leaked a terrific amount of gas, which I mostly expected, though I didn't quite expect for the amount of crisp bacon-like breakage that immediately occurred... Hooray for well ventilated spaces.

    Time to replace everything with FI rated clamps and lines, which the car probably doesn't have (definitely has the slotted band-type clamps, which I've been told not to use), and I was bound to do anyway

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