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Thread: Fuel tank vent

  1. #26

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    This all varies somewhat, depending on the style of canister you have. If it's the stock '85 style, then
    it will have a sort of "F" connector on one port, and a mushroom cap on the other. The fuel bowl vent
    hose will connect to the larger diameter nipple on the F connector, and everything else connects to
    the smaller nipple, using tees as required. For your setup, that will pretty much be just the tank vent
    line, and the canister port on the purge valve. Pretty simple.

    Again, this post shows what goes where on the purge valve -
    http://vb.foureyedpride.com/showthre...074#post740074
    Where it says ported vacuum, that will be EGR vacuum in your case. (Ported for engines that don't
    have an EGR vacuum source.)

    The purge system does not pull a vacuum on the tank, because that mushroom cap on the other port
    on the canister lets air in, to purge the vapors.

    You are correct that you do not want to connect up the bowl vent until you have a vent solenoid for it.
    The vent solenoid closes when the ignition is on, so the fuel bowl pressure is referenced to the inside
    of the air cleaner. You will also want to cap the unused larger nipple on the F connector.
    Last edited by JACook; 03-12-2016 at 10:59 AM.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  2. #27
    FEP Member Mgino757's Avatar
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    Well, unfortunately, the F connector is damn near impossible to find. I had some hose for the fuel bowl vent sitting around. Fortunately, the OD of the hose fits perfectly into the vapor canister and is a tight enough fit to hold vacuum, I had the proper vacuum adapters to make it work. As it currently sits, I have the fuel tank vent going to the canister. That very same hose is tee'd to one of the lower ports on the purge valve. The other lower port (middle) is connected to manifold vacuum. The top, smaller port is connected to the EGR nipple on the front of the carb. Seems to be working well so far. Of course, I am missing all of the vacuum delay and vacuum restrictors, so it is all hooked up, straight up.
    1985 Mustang GT conv. modified 4180C, Weiand Street Warrior intake, equal length headers, true dual exhaust, 3.55:1 8.8'' rear end, 2003 V6 T5, Ford Racing 10.5" clutch.

    1998 Mustang GT auto. PI swapped. Daily beater

  3. #28

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    Ford trucks from '77-'80, and cars from '78-'80 used a purge valve that plugs directly onto the
    canister, with nipples for the tank and bowl vent hoses on it. Might be a little easier to find than
    the F fitting. Then again maybe not.
    Cheers,
    Jeff Cook

    '85 GT Hatch, 5-speed T-Top, Eibachs, Konis, & ARE 5-Spokes ... '85 GT Vert, CFI/AOD, all factory...
    '79 Fairmont StaWag, 5.0, 62K original miles ... '04 Azure Blue 40th Anny Mach 1, 37K original miles...
    2012 F150 S-Crew 4x4 5.0 "Blue Coyote"... 65 coupe, 289 auto, Pony interior ... '67 coupe 6-cyl 4-speed ...
    '68 Vert, Mexican block 307 4-speed... '71 Datsun 510 ...
    And a 1-of-328 Deep Blue Pearl 2003 Marauder 4.6 DOHC, J-Mod, 4.10s and Lidio tune

  4. #29
    FEP Member Mgino757's Avatar
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    I Mac Guyvered a solution by slipping a hose into the canister and using a few adapters of various sizes. Pics are worth 1,000 words so I snapped a few of how I laid it out. I really want to find a vacuum delay valve for the evap system, but this is it for now.

    The hose fits snug as a bug


    The big hose necks down to a size useable by the evap control valve






    my purge line connected to the evap control valve


    TAB/TAD solenoid connections with evap system tee'd into the EGR feed on the carb


    evap and thermactor system connections


    spark port connection


    Ported vacuum switch that controls the spark advance


    Who can resist a nice motor shot? lol


    I more or less used this as a loose guide for setting up my vacuum system based on what I still have.
    1985 Mustang GT conv. modified 4180C, Weiand Street Warrior intake, equal length headers, true dual exhaust, 3.55:1 8.8'' rear end, 2003 V6 T5, Ford Racing 10.5" clutch.

    1998 Mustang GT auto. PI swapped. Daily beater

  5. #30
    FEP Member Mgino757's Avatar
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    Quote Originally Posted by JACook View Post
    Ford trucks from '77-'80, and cars from '78-'80 used a purge valve that plugs directly onto the
    canister, with nipples for the tank and bowl vent hoses on it. Might be a little easier to find than
    the F fitting. Then again maybe not.
    thanks for the info! I hit up Rock auto and I was able to find a listing for the brown/black vacuum delay valve. I might even get that particular purge valve too.

    EDIT: What would you suggest as a suitable vacuum delay time for evap and thermactor systems? Should I also put on the the distributor vacuum advance connection?
    Last edited by Mgino757; 03-15-2016 at 01:33 AM.
    1985 Mustang GT conv. modified 4180C, Weiand Street Warrior intake, equal length headers, true dual exhaust, 3.55:1 8.8'' rear end, 2003 V6 T5, Ford Racing 10.5" clutch.

    1998 Mustang GT auto. PI swapped. Daily beater

  6. #31

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    Quote Originally Posted by JACook View Post
    The vent solenoid closes when the ignition is on, so the fuel bowl pressure is referenced to the inside
    of the air cleaner.
    I can't seem to wrap my head around this. I have seen this written before, but I don't understand what it means. Will you humor me and break this down further?

    Perhaps part of the lack of understanding on my part is I have a 1965 Mustang with the stock Autolite 4100 carburetor. The Autolite has a much smaller external bowl vent on the top of each fuel bowl that is always open. (And there is always a little bit of dried gas stains around these vents.) Unlike the Motorcraft 4180 I have on my 1985 Mustang, the Autolite 4100 doesn't have a hose with a vent solenoid that closes when the ignition is on. Does that mean the fuel bowl pressure is referenced to the inside of the air cleaner AND outside the air cleaner? Is this less desirable in some way? Both cars run great.


    And why is it that the hose that vents the gas tank is so small, and the hoses that vent the fuel bowls are so large? You would think it would be the other way around, considering how much more gas is in the gas tank compared to the fuel bowls?
    Last edited by RickFury; 06-15-2019 at 10:32 AM.

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