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SU fuel lines and low pressure pump

This is a discussion on SU fuel lines and low pressure pump within the SU Carb Discussions forums, part of the SU Carb Central category; I'm trying to figure out how I should route the fuel lines from a new inline, low pressure fuel pump ...


  1. #1
    Registered User supraman's Avatar
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    Default SU fuel lines and low pressure pump

    I'm trying to figure out how I should route the fuel lines from a new inline, low pressure fuel pump to a set of SU's. Keep in mind I'm about clueless when it involves classic imports or carbs for that matter. The oldest car I have is my 87' turbo Supra.
    I am no mechanic either but I am really trying to learn through research and asking questions.
    The questions-
    I just run the fuel lines from the tank, into an inline filter, to the pump, then to my su's right?
    I just have a custom set of daul polished SU's on my 77 280z that have been rebuilt and the lines have been modified on the SU's.
    The fuel lines look to be conected into a (two to one line) by a series of t-fittings and fuel hose. Do I just run one line from my fuel pump to this?
    I noticed there are two lines like that on the carbs also.
    One is smaller than the other but both are two into one setup.
    I'm so lost and retarded to carb's.
    I figured out the linkage and have it smooth.

    I just run the wiring from the switch to a relay then to the inline fuse then where?
    Can someone please help me with some good links or advice please?



    I also want to run the new fuel pump on a switch and to the battery.

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    Semi-retired admin Arne's Avatar
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    I've attached a schematic of the fuel piping layout for an early 240Z. Bear in mind that many 240Zs had no electric pumps at all, just a mechanical pump mounted on the cylinder head.

    The electric low-pressure pump is best mounted in the same location as the high-pressure pump your car came with, right in front of the tank.

    On a 240Z (and I assume on a 280Z as well), there are two metal fuel pipes both running between the tank and the right inner fender, in front of the wheel. (The pipes may terminate somewhere else in the 280Z engine bay, I don't know.) There is a larger pipe (fuel from tank to carbs) and a smaller diameter pipe (excess fuel return). The fuel supply pipe goes to a filter, and from there to the pump on the head, which pumps directly into the fuel rail and to the carbs. The excess leaves the fuel rail and goes back to the return pipe on the inner fender and then back to the tank.

    In your case, the pump will be at the rear pulling fuel from the tank and into the bigger fuel pipe. You should probably mount an inline filter before the pump, and a second filter somewhere between the supply pipe and the fuel rail is a good idea as well.
    Attached Thumbnails Attached Thumbnails SU fuel lines and low pressure pump-picture-1.png  
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    Registered User Walter Moore's Avatar
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    Here is a thread showing how I installed my electric fuel pump.
    Holley fuel pump installation

    By the way, don't use the glass style fuel filters shown in the pictures in that thread. Eventually they both cracked and had to be replaced with metal cased filters.
    '71 240Z, Because any fool can drive fast in a straight line.

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    Thanks Arne,
    That helps alot, the only thing is my 280Z has 3 feul lines so i gues I can just eliminate 1 line, use one as a return, and the other as the main fuel sending line.
    Now I just need to figure out how to wire it up to its own switch.
    Thanks again,I was kinda winging it till now.

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    Registered User supraman's Avatar
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    Quote Originally Posted by Walter Moore View Post
    Here is a thread showing how I installed my electric fuel pump.
    Holley fuel pump installation

    By the way, don't use the glass style fuel filters shown in the pictures in that thread. Eventually they both cracked and had to be replaced with metal cased filters.

    Thank you very much for the advice.
    It's a shame, because thats the first filter I bought was the glass one.
    I'll get a few inline billet one's instead.
    Good looking out man!
    Thank's for the link too, I'll read up.
    Last edited by supraman; 03-27-2009 at 11:20 AM.

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    Semi-retired admin Arne's Avatar
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    Quote Originally Posted by supraman View Post
    ...the only thing is my 280Z has 3 feul lines so i gues I can just eliminate 1 line, use one as a return, and the other as the main fuel sending line.
    That third line might be the evap vent tube. The diagram doesn't show it since it's not a fuel line, as such. On a 240Z it runs from the evap tank inside the car to a flow valve on the left inner fender near the coil. Again, I don't know how that compares to the 280Z system, but I assume that there may be a similar line for that.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    To an aspiring geezer (in marked contrast to an EXpiring geezer) like myself, it's just so refreshing to hear someone say that they are baffled by carbs. To me, they're second nature and I wouldn't want to be responsible for anything that relies on those infernal EFIs and computer chips. Turbos... Gaah.
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    Semi-retired admin Arne's Avatar
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    There's really no difference. Measure the air flow and deliver fuel to match. The EFI air/fuel map is in bytes, for SUs it's the taper of the needles. I can't read either one by eye.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    Quote Originally Posted by Arne View Post
    There's really no difference. Measure the air flow and deliver fuel to match. The EFI air/fuel map is in bytes, for SUs it's the taper of the needles. I can't read either one by eye.
    I would have to say that EFI is mainly for power, turbo's, etc.
    But my Z is 6 years older than I am so carb's just seemed like the thing to do.
    I figure, add some vintage, in a vintage car, rather than create a death trap of a car that has open diff in the rear.
    My Supra holds the road about 100% better and is lower to the ground.
    It's an MK3 87 turbo model with a butt ton of mods.
    All EFI!
    The original Z just looks better with carbs and if it runs good with them then why not!?

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