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  1. #1
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    Running rich and stalls at idle

    Hello!

    I just got a Zagato, and I must say that I'm grateful for this forum.

    I got the timing belt changed and finally fired it up. Exhaust sounds pretty good for a four.

    It will run at high idle with a bit of stumbling, and will run at mid idle. But stalls at idle once choke opens. Exhaust smells very strong (rich I believe). Haven't been able to pin point vacuum leaks.

    I used to have a feedback carburetor on an 87 Mazda. But I think this completely mechanical emissions setup is worse.

    Any suggestions would be appreciated.

    Thanks!

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    Re: Running rich and stalls at idle

    Just another thought. If I were to simply start disconnecting vacuum hoses and plugging the ports, is there any sensible way to go about it? Could I get the manifold and carb to bare bones to see if it will run right and then work backwards? How much of that emission stuff is involved with proper running?

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    Re: Running rich and stalls at idle

    Second post here covers adjustment for this type of carb pretty well:
    https://xwebforums.com/forum/index.p...settings.4140/

    A while ago I figured out they met emissions standards by reducing compression, using a too-small carburetor, and adding a catalyst, EGR, and secondary air induction/injection to the exhaust stream. The rest of that "emissions" stuff was really just compensation to improve running and drivability under various special-case conditions with an undercarbureted low-compression engine.

    You could actually have a lean misfire caused by a vacuum leak, which would cause a rich-smelling exhaust. If you have emissions testing or a shop that can do exhaust gas analysis, a lean misfire would show high hydrocarbons (HC) but low carbon monoxide (CO), whereas running rich would show HC and CO both high. If you don't spot any missing/split vacuum caps, you can try spraying carb cleaner around various spots until you hit one where it raises the idle, or use an unlit propane torch with a length of hose you can wave and poke around until it affects the idle.

    If you don't have emissions testing, ultimately you will probably want to upgrade to a Weber 34 DAT/DATR carb, which also requires swapping to an Beta 1800 ('75-78 ) intake manifold. This is the proper Euro-spec carb for the engine size, and will allow you to eliminate most of the vacuum lines.
    Last edited by SubGothius; 21st September 2019 at 06:22 PM.
    Best regards,
    -Tye (1979 Lancia Beta Zagato spider)

    "In theory there's no difference between theory and practice, but in practice there is."
    -Jan L.A. van de Snepscheut

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    Re: Running rich and stalls at idle

    Hi, and thanks for the reply.

    Now that I think about it, the exhaust smell isn't properly rich. I don't see any black fumes. And in all likelihood, a vacuum leak is much more probable than anything else.

    We don't have emissions testing where I live, so I can modify. But I have the Zagado with the tilted engine. Will a straight 1800 manifold work? That would tilt the carb right?

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    Re: Running rich and stalls at idle

    One more thing: if yours has a pulley on the end of the intake cam driving an air pump, you have the California emissions setup; if you don't have that pulley, you've got 49-state Federal emissions.

    All Betas (incl. Zagato and Scorpion) have the engine tilted back, so you'd need to use a Beta manifold, as Fiat manifolds would not be angled properly to keep the carb level.

    The '79-only Beta manifold has intake ports matched to the undersized barrels of the stock DHTA 30/32 carb, and can't readily be modified to make good use of any larger carb; it's also a "dual-plane" design that flows less efficiently than the single-plane type fitted to the Euro and earlier 1800 models, like this one:
    https://www.ebay.com/itm/Lancia-Beta...d/332749717511

    Your '79 stock manifold has 4 vac ports:
    1. Tiny one on top of #1 runner, feeds carb power valve, vac accelerator pump, warm-air flap in air cleaner housing, and Cali air pump control;
    2. Small one at front center, controls gulp valve and feeds vac reservoir for HVAC controls;
    3. Large one at front off-center, takes surplus air intake from the gulp valve attached to the battery tray (prevents backfire on abrupt deceleration);
    4. Big one on top of #4 runner, forked to feed brake booster and A/C fast-idle capsule on the carb.

    For troubleshooting you can safely cap off all of those except of course the booster line on #4.

    Your '79 stock carb should have 6 vac ports:
    1. Front of carb base, takes PCV vapors from a barb where the big PCV hose attaches to your air cleaner housing;
    2. Back of carb base, takes fuel vapors from the charcoal canister under the brake master cylinder;
    3. Back of carb body angled towards EGR valve, controls EGR via a thermovalve in the manifold;
    4. Back of carb body angled towards distributor, controls the vacuum advance via a delay valve and thermovalve;
    5. Upper side of carb body, vacuum accelerator pump;
    6. Lower side of carb body, power valve.

    Of those, #4 can safely eliminate the delay valve and thermovalve, thereby feeding vac signal directly from carb to distributor advance; this may result in some stumbling when cold.

    #5 enriches the mixture in response to vac demand when the engine is cold; vac to this is blocked when warm by the green thermovalve in the lower coolant pipe from the radiator.

    #6 enriches the mixture at full throttle or high cruise, or when the engine is cold; high vac signal closes this valve, and this vac is blocked when cold by the yellow thermovalve (in a series of them alongside the lower coolant pipe, all of which block vac when cold).
    Last edited by SubGothius; 16th October 2019 at 05:58 PM.
    Best regards,
    -Tye (1979 Lancia Beta Zagato spider)

    "In theory there's no difference between theory and practice, but in practice there is."
    -Jan L.A. van de Snepscheut

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    Re: Running rich and stalls at idle

    My goodness, thank you for so much information. I'm going to start troubleshooting.

    Mine does not have the air pulley, just the passive induction.

    If I were to use a manifold like the one you referenced, and then got a Weber 34 dat, do you have any suggestions on how to retro fit the evaporation system/coolant setup/delete EGR?

    Thank you.

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    Re: Running rich and stalls at idle

    The 1800 manny has no EGR provision, so then you'd just need to remove the EGR pipe and plug that bung in your stock exhaust manny somehow. The 34 DAT has a water choke, so your existing coolant flow should just swap right over to that. I think it should also have a barb in the base for evap vapor capture.
    Best regards,
    -Tye (1979 Lancia Beta Zagato spider)

    "In theory there's no difference between theory and practice, but in practice there is."
    -Jan L.A. van de Snepscheut

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    Re: Running rich and stalls at idle

    Ok, so the coolant flow in both intake manifold are the same?

  9. #9
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    Re: Running rich and stalls at idle

    Quote Originally Posted by Ben D View Post
    Ok, so the coolant flow in both intake manifold are the same?
    Correct.
    Best regards,
    -Tye (1979 Lancia Beta Zagato spider)

    "In theory there's no difference between theory and practice, but in practice there is."
    -Jan L.A. van de Snepscheut

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