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  1. #1

    Default 4bbl GT emissions 83 vs 84/85

    I've been using my car as a reference ('83 GT original stock 5.0L 4v) and researching old threads about the some emissions systems when I found this thread on the WOT switch and canister purge solenoid activation.

    http://vb.foureyedpride.com/showthre...ght=WOT+switch

    On my 83, the CanPurge solenoids activate when ignition is ON the block hoses from the carb bowls to the charcoal canisters (good thing).
    But, the solenoids will deactivate when the WOT switch is "pressed" at full throttle (bad thing).

    The CanPurge solenoids should be wired to the hot side of the WOT switch and not the "switched" side of the switch. (?)

    84 and 85 models got this right but 83's are wrong ? (from Ford ?) and bottom line is the bowl vents should not be opening at WOT. (?!?)

    The correct function of the WOT switch is to activate the bypass solenoid at full throttle/high rpm... which cuts vacuum to the bypass valve which vents smog pump air to the atmosphere at high rpm/full throttle. This is what my car does anyway.

    Thanks

  2. #2

    Default

    I'm not sure what you're trying to figure out, but will argue that pressing the throttle to full throttle is a bad thing.
    Mike
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website ---> http://carb-rebuilds-plus.boards.net/

  3. #3

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    I guess I'm trying to "stick it to the man" (Ford)...

    64 dollar question:
    Is it correct that the carb bowls should never be vented to outside the of the air cleaner (through the canister purge solenoids) when the engine is running ?

  4. #4

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    Quote Originally Posted by jessesandy View Post
    I guess I'm trying to "stick it to the man" (Ford)...

    64 dollar question:
    Is it correct that the carb bowls should never be vented to outside the of the air cleaner (through the canister purge solenoids) when the engine is running ?
    Yes that is correct. I still contend that it never was wrong on bbcjay's '83. Unless someone can actually confirm that
    the WOT switch is cutting power to the bowl vent solenoids on their '83 5.0, I call BS. Wiring diagrams are not proof
    of anything.
    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

  5. #5

    Default

    I was experimenting/learning the system by pressing the WOT switch while blowing thru the bowl vent hose. ('83 GT 5.0L 4bbl)

    Ignition Off... can blow thru hose.
    Ignition On... cannot blow thru hose.
    Press and hold WOT switch... can blow thru hose again.

    And you can feel them clicking when the WOT switch is pressed/released also.

  6. #6

    Default

    OK so we need to understand why that's happening, because it should not be. It may be that the WOT alternator
    cutout TSB was improperly done, or some other wiring error exists.

    Take a look at the WOT switch connector. On one side should be a single red/yellow hash wire. On the other side
    should be a single solid red wire. Both of these wires join into the chassis harness in a grey 8-pin connector near
    the ignition module.

    There should be continuity between the bowl vent solenoid connectors, and the red/yellow hash side of the WOT
    switch connector, with the WOT switch disconnected. There should not be continuity between the bowl vent solenoid
    connectors and the solid red wire side of the WOT switch connector, likewise with the WOT switch disconnected.

    Also, with the WOT switch disconnected, check for continuity between the red/yellow hash wire, and the light green/
    red stripe wire on the voltage regulator 'S' terminal. You should see continuity if the TSB was not done. If the TSB
    was done, you would see continuity between the regulator 'S' terminal and the WOT switch connector solid red wire
    instead.

    Verifying these conditions will give us a starting point, to figure out where to look next.
    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

  7. #7

    Default

    The wiring itself is easy enough. I'm still learning how the smog systems are supposed to work.
    As for the canister purge/bowl vent solenoids. They were wired to the "switched" side of the WOT switch in stead of the hot/ignition on side.
    Don't know if it came that way or I did it by mistake when repairing/rebuilding the wiring back in the 90's.

    Now for the TAD valve.
    The thermactor diverter solenoid is controlled by the WOT vacuum switch (behind the driver side shock tower) which activates at 8" vacuum.

    When manifold vacuum 20 to 8 (idle to cruise), the TAD solenoid is off and the TAD valve responds to egr vacuum.
    If there is enough egr vacuum, the diverter valve will send air downstream to the cat.

    When manifold vacuum is 8 to 0 (heavy load to WOT) the vacuum switch activates the TAD solenoid.
    Now the diverter valve is vented to atmosphere and smog pump air is sent up stream to the heads.

    Am I on the right track ?

    Thanks.

  8. #8

    Default

    You're on the right track conceptually, but took a slight detour getting there.

    The descriptions of these systems can be somewhat confusing, having to do with the definition of 'above' and
    'below', when we're talking about negative pressures (aka 'vacuum'). Technically, 5 in/Hg vacuum is less negative
    than 10 in/Hg of vacuum. Kinda like how 4.10 gears are 'lower' than 3.55s...

    Operationally, it is as you say. At idle and light throttle openings, the TAD system is under control of EGR vacuum.
    But the TAD solenoid is energized in this mode. Both TAB and TAD solenoids are normally closed at rest, while the
    TAB vacuum switch is normally open at rest (atmospheric pressure).

    <edit>
    After further review, the '85 TAD solenoid is normally open, and the '85 TAD vacuum switch is normally closed.
    Apologies for the misinformation...
    </edit>

    At idle, EGR vacuum is weak, so the diverter valve sends air upstream to the exhaust ports. At light throttle openings,
    EGR vacuum is strong, and the air is sent downstream between the beds in the main catalyst. This reduces exhaust
    temperatures in the upstream light-off cats, while also maximizing NOx reduction.

    With heavier throttle openings, where manifold vacuum is 10 in/Hg or 'less', the vacuum switch opens, de-energizing
    the TAD solenoid. This blocks EGR vacuum, and vents the diverter valve, sending air upstream into the exhaust ports,
    until manifold vacuum drops low enough that the bypass valve opens and thermactor air is dumped to atmosphere.
    The TAD system works essentially the same for '83-'85 4V engines, the main difference being the '85 vacuum switch
    transfers at 6 in/Hg, vs 10 in/Hg.

    As an additional safeguard, the TAB solenoid is under control of the WOT switch on '83 and '84 4V engines. The TAB
    solenoid is de-energized at WOT, blocking manifold vacuum to the bypass valve. (For '85 4V engines, the TAB solenoid
    is controlled by the TSAD module, which does the same thing, but will also shut off the air supply during extended idle
    periods.)
    Last edited by JACook; 01-21-2017 at 08:51 PM. Reason: Corrections and additions
    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

  9. #9

    Default

    Thanks. Although my components are operating in reverse to achieve the same operation.
    My '83 is an early build (Oct. '82). (if that might explain the differences ?)

    Anyway, my vacuum switch is definitely closed (13.2 ohms) at atmosphere (from 0 to 8 inches)
    and the goes to open circuit with 8 inches or more.

    Name:  WOT vacuum switch.jpg
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    Also, my TAB and TAD solenoids "pass through" vacuum when they are not energized.
    When energized the solenoids block the source vacuum and vent the "device" to atmosphere.

    The end result is operation just as you described.

    What is the reason to send thermactor air upstream during heavy load ?

    Thanks
    Todd H.

  10. #10

    Default

    Anyway, my vacuum switch is definitely closed (13.2 ohms) at atmosphere (from 0 to 8 inches)
    and the goes to open circuit with 8 inches or more.

    Your switch is bad. You should have 0.0 to 0.2 ohms across closed
    contacts. 13.2 ohms is indicating that the contacts are ether dirty or pitted and are not making good contact which will cause a voltage drop through the switch.

  11. #11
    FEP Member Mgino757's Avatar
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    Default

    Good luck finding another switch though.
    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

  12. #12

    Default

    Quote Originally Posted by Mgino757 View Post
    Good luck finding another switch though.

    If you just want something that functions then you could use one of these.



    I bought mine from Superior Transmission #K058 but it's actually a World Magnetics #PSF109S-81-330 so you may be able to find it cheaper if you cut out the middle man.

  13. #13

    Default

    Wish it was better, but not effecting the circuit enough to be a problem. Hope it doesn't get worse.
    (Good to know there are replacement options available)
    Unfortunately it is sealed so I can't easily "De-Ox-It" like I have been doing to resurrect the rest of the electrical systems on the car.

    Does verify that it is a normally closed switch vs. normally open. (No readable part numbers on it)

    Edit:
    This is a good example of way folks should not use a continuity tester or the continuity function of a multimeter.
    IIRC a Fluke DMM will "beep" for continuity up to 40 ohms.
    Last edited by jessesandy; 01-21-2017 at 05:21 PM.

  14. #14

    Default

    Thanks for the additional data points. Documentation for these systems is pretty spotty, especially for the earlier
    5.0 HOs. Though with your confirmation, I went back and was able to find some additional documentation on the
    earlier TAB and TAD solenoids. I also went back and verified my notes, and discovered they weren't entirely
    accurate.

    What I found is that the dual thermactor solenoid assemblies come in at least 3 types - Both normally closed,
    both normally open, and one of each. It appears '85 is the odd one in the group. The '85 solenoids are actually
    the 'one of each' variety, with the TAD solenoid being normally open, and TAB normally closed.

    The '85 vacuum switch that controls TAD is a different switch from yours, which I knew because it's green, and
    transfers at 6 in/Hg, but I can now confirm it is also NC.

    The reason we switch back to upstream air during moderate acceleration has to do with how the switch roughly
    coincides with the carburetor's power enrichment circuit. The OE 2-stage power valve starts to enrich the fuel
    mixture around 10-10.5 in/Hg. The richer mixture lowers peak combustion temperatures, so less NOx reduction
    is needed. Bby switching the supplemental air upstream, all available catalyst beds can run in oxidation mode.
    This also helps cleanse the 3-way catalyst beds, improving their NOx reduction efficiency.

    I would not assume your resistance readings mean the switch is defective. I've got a '79 vintage black vacuum
    switch that was used to control a yellow-grommet Duraspark module, and it's got an inline resistor to one of the
    connector pins. I don't know if it is, but yours -could- be wired up with resistor wire. I would pierce the wires
    close to the switch, and re-check the resistance to be sure.

    The switches can be found on Ebay, though you may not find the exact same one with the same bracket and/or
    connector. But the original switches are color-coded to denote the vacuum level, and whether NO or NC. Any
    black body switch should be functionally equivalent to yours, and could be combined with your existing connector
    and bracket without too much effort. Search for base part number 12A182 or 12A265.
    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

  15. #15
    FEP Member Mgino757's Avatar
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    Those part numbers are pretty helpful. I have been hunting for these switches forever. The 12A182 has 3 switches, but it looks like my 85 GT came with two. Would those switches still work for my thermactor system? How about the shift light? Any idea what the part number is that the 85 4bbl GT's came with?

    These are the connectors that are behind my driver side strut tower.

    Name:  FB_IMG_1483501576371.jpg
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    Last edited by Mgino757; 01-26-2017 at 10:23 PM.
    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

  16. #16
    FEP Member Mgino757's Avatar
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    Any light on this?

    I was just able to find a 12A182 black bodied switch for my 85, so I snagged it up. At least I can get the thermactor system up and running.
    Last edited by Mgino757; 02-28-2017 at 06:17 PM.
    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

  17. #17

    Default

    I've looked all over the internet and couldn't find any mention of this vacuum control switch at all on any Ford vehicle. And then gave up.

    Your car is missing the switch all together ?

    I don't recognize the 3-pin connector in your picture. Either didn't come on an '83 or I rewired it years ago.

  18. #18
    FEP Member Mgino757's Avatar
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    Apparently, there was a dual vacuum switch assembly that came on mine, but one of the previous owners took it out along with the high altitude compensation system.
    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

  19. #19
    FEP Member Mgino757's Avatar
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    Well, I was supposed to receive the vacuum switch on Saturday, but I never got it. USPS tracking says it was delivered, but I got nothing. Go figure, I get close to getting the right thing, and something screws that plan all 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

  20. #20

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    Hope it turns up.

  21. #21
    FEP Member Mgino757's Avatar
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    It arrived today. Thank goodness. Got the one shown in the picture above, black body vacuum switch. I know it isn't the correct one, but it will suffice. Now my Thermactor system is up and working again, in a rudimentary fashion. I just need some vacuum resistors and delay valves to make it slightly closer to correct.
    Last edited by Mgino757; 03-08-2017 at 09:26 PM.
    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

  22. #22
    FEP Super Member xctasy's Avatar
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    Nice work.

    The only reason this works is that you've learned the rules, and have all talked and gotten to know Whats What. If it was a 3.8 CFI, you might not ever get To the point you have with your 5.0

    Missing Smog gear is the kinda jam registration officials love to argue over. Emissions equipment removal in a figurative sense attracts Wasps. Not White A****S*****P*******s but the Smog Nazi Yellow Jacket Kind.


    No one touches you if you use the right stuff, it just sends em packing. Biats them, traps them, gets em off your back.


    But have you all noticed how hard putting a Giant Jam Sandwhich back together is when some SOB has taken all the Emmissions Jam away...emissions gear removal is just such a trap. Not one part reduces performance.


    Its the other emissions test constraints,
    low compression,
    higher back pressure exhausts,
    a lack of braveness in the cam timing,
    conservative ignition ramps,
    the love of ported to manifold vacum transfers
    air cleaner heat stoves and vac motor control systems.


    They sit there waiting for some porr dumb a## to remove one part, and the whole system falls like Jenga.

    Then all othe acres of emission line laughes at you like a big medusa, and goes on attack.


    For times like these, a good read helps. Hope you like and are confused by its relevance...I do like to stir up a hornets nest.....

    https://www.youtube.com/watch?v=Iiv4AbrRsww


    Good luck, Mgino757

    Illegitimi non carborundum, from Deano.



    PS Walking-Tall, aint gettin at ya, love your 3.8 emissions removal too, especially on what was the only bad system Ford ever made, the 3.8 set up....At least you don't have emmissions wasps in your state for 30+ y/o cars...If some one from Ford would please like to explain why they made the 82 to 86 era 3.8 system so bad......if it wasn't bad, your car would be doing sub 18 second 1/4 miles and 30 mpg like all V6's should.

  23. #23

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    For times like these, a good read helps. Hope you like and are confused by its relevance...I do like to stir up a hornets nest.....
    https://www.youtube.com/watch?v=Iiv4AbrRsww

    Would have been better with the voice from Dr. Seuss.
    Last edited by jessesandy; 03-09-2017 at 01:05 PM.

  24. #24
    FEP Super Member xctasy's Avatar
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    Yup, Pommy gits....LOL. Ya know, they drive on the left?

    I've tried driving on the right in my LHD car, but there's too many others driving on the wrong side....

    https://www.youtube.com/watch?v=dF28H45b1Zk

    This is what emissions gear does to you....creates a pile up.

    https://www.youtube.com/watch?v=XanuTkC3HAc


    Mgino757 Hope your Black body vacuum control switch does the job

  25. #25
    FEP Member Mgino757's Avatar
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    So far so good. Cats don't seem to be over heating, even after long highway trips. I get a pop every now and then in the exhaust when the engine is still warming up after I get heavy on the throttle and let off, which is to be expected with rich mixtures and a lack of the proper vacuum delay valves and vacuum restrictor tubes. I'm also fine tuning the choke settings. Now that I have the fast idle settings adjusted correctly, I just have to reduce my "choke apply" time a bit.

    Most fox owners we know, the first thing they do is rip all this stuff out and throw it in the trash. Someone did that with most of the stuff on my car. It came with the high altitude compensation system, which is now long gone. The vacuum switches that limit when the upshift light comes on, all long gone. Trying to find this stuff now is pretty time consuming, if not, darn near impossible since no one makes the components anymore and no one ever saves them. I like having stuff working as it should. Until I change the cylinder heads, this fox will have a working smog pump system.
    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

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