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Carburetor Question???

Discussion in 'F-J-M: Volare, Diplomat, etc, 1977-89' started by goair99, Jan 8, 2017.

  1. goair99

    goair99 Active Member

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    20170108_105331.jpg What position should the choke plate be in during 1) Cold start? and 2) Normal operating temp?
    I think my choke is not closing during normal warm driving and the air filter is soaked with fuel.

    Also no suction at PCV

    Pic is of idle at normal operating temp:
     
  2. LouJC

    LouJC Active Member

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    That is how it should be at normal temp. It should close for a cold start, and then be pulled open a fraction of an inch by a vacuum motor to allow just enough air to keep the engine running. As the engine warms up it should gradually open. No suction at the PVC (valve or hose?) could be a stuck valve (they do get gummed up) or clogged hose or vaccum port on the intake manifold. Gas soaking the air filter, is a concerning problem because if the engine backfires, it could set the air filter element on fire. Better find out why that's happening.
     
    Doug D likes this.
  3. goair99

    goair99 Active Member

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    Thanks LouJC for your quick reply, I will have my mechanic check out the soaked air filter. BTW no suction at end of valve, and it does rattle also???
     
  4. Doug D

    Doug D Virginia Gentleman

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    Lou beat me to it. Cold start the plate should be 99% closed. As it warms it should open. During a warm or hot start the choke plate should be open.

    PCV's do fail and get gummed up. Probably needs to be replaced. A PCV can rattle and not work.

    Gas in the air filter is a separate issue I believe.
     
  5. goair99

    goair99 Active Member

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    Can anyone venture a guess as to why the air filter is damp with fuel? It is not dripping wet, but there was fuel on the top of the cover and the rubber seal on the filter. The car does sit a lot and has a rebuilt carb on it. It seems to run fine both at cold start and normal driving...
     
  6. ImperialCrown

    Level III Supporter

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    After a hot engine shutdown, give it a few minutes and then remove the air cleaner lid. Do you see fuel misting or percolating?
    Is the bowl vent clear and properly adjusted?
    The wetness may be blowby from the crankcase breather. With the PCV not working, the pressure will push blowby into the air cleaner. It may stink like gasoline and vapors still may be flammable, but it is mostly dirty, stinky condensate with a little oil mixed in.
    Can you blow through the PCV hose? A wrong carburetor base gasket can also block PCV vacuum if the hose leads to the carburetor base.
     
  7. LouJC

    LouJC Active Member

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    I was thinking that there could be a relation between the lack of vaccum at the PVC and the wet air filter element, but for it to smell like gas is a bit unusual. Usually there is a small filter that is inside the air cleaner lower housing, that filters air going into the valve cover to make up for the blow-by being sucked into the engine by the PVC system. I wonder if this little filter is missing?
     
  8. valiant67

    valiant67 Rich Corinthian Leather
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    PCV fumes can smell like gas. It's very difficult for gas to get to the air filter element.
     
  9. dana44

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    If the float is too high, but still low enough to not fully overflow, it could splatter a little bit, but you have a smaller air vent and probably not likely. One thing that could happen, and I did have this issue, an intake valve spring was broken and a small amount of blowback from the intake pushed fuel splatter out the carb. Believe it or not, it was my TR4 engine, dual sidedraft DCOE 42 Weber carbs and it spurted like that for two years and never came apart. Wasn't until about five years later I noticed the valve spring was broken, but the windings were so tight, it never came apart. Lucky me.
     
  10. goair99

    goair99 Active Member

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    Thanks again to you all! I will check out the PCV, hose and base of carb and let you know...
     
  11. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    My bet on the PCV system is that someone connected the hose to the wrong port, one above the throttle plate.
     
  12. dana44

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    At the same time, when PVC is in wrong position or hose/valve plugged, a lot of extra blow-by comes out the breather cap, and rarely do they idle properly.
     
    Bob Lincoln likes this.
  13. goair99

    goair99 Active Member

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    Which port? The one at the base of the carb facing forward?
     
  14. valiant67

    valiant67 Rich Corinthian Leather
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    It varies by carb design. is this on the 1989 Chrysler Fifth Avenue?
    you should have a vacuum diagram under the hood showing which hoses connect where.
     
  15. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    PCV hose goes on one of the larger ports on the carb base, BELOW the throttle plate. If you have power brakes, there may be another large port below the throttle plate, or that hose might connect directly to the intake manifold. PCV hose never connects to a port above the throttle plate.
     
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  16. goair99

    goair99 Active Member

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    When you say throttle plate, do you mean at the base of the carb??? I will get some more pics tomorrow morning when I take the air filter housing off.
     
  17. GLHS60

    GLHS60 Well-Known Member

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    When you remove the air cleaner in the morning the choke blade should still be open.

    Due to the fast idle mechanism you will need to press the accelerator to allow the choke close.

    You can move the carb linkage by hand and watch the choke close before starting.

    Engine off of course!!

    Thanks
    Randy
     
  18. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Yes, carbs have a choke plate at the top, and throttle plate at the base.
     
  19. goair99

    goair99 Active Member

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    OK you all. Whoever replaced the carb on my car has some of the hoses hooked up wrong! According to the emissions routing diagram, the PCV hose is hooked up to where the vapor canister hose is supposed to go and one hose is missing period. I have no idea what is hooked up to where the PCV hose is supposed to go. Will figure this out tomorrow morning, when I take the air filter housing off completely.

    Anyone know what diameter hose is used for the vapor canister? Stay tuned...
     
  20. LouJC

    LouJC Active Member

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    Post up some pix, if someone has an old factory shop manual you can find out the vaccum hose routing that way, or even a Haynes manual may have it. Now what you described makes sense actually, fuel vapors for sure can come from the evap recovery system and condense in the air filter. This is dangerous as I said before because if the engine ever backfires through the carb it can set the air filter on fire. Note to self: when working on the engine, always replace the top of the air cleaner housing before starting up. Do not look down the carb throat when someone else tries to start it just in case.
     

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