Auto choke working the wrong way around
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  1. #1
    nJm
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    Auto choke working the wrong way around

    As some of you might remember I swapped the Solex on my car for one from a slightly newer 505. Anyway, what I have noticed is that the choke on this one works the wrong way around. When the car is cold it idles around 850-950 rpm. Once it has warmed up it will idle between 1200rpm and 1500rpm.

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    Any suggestions? I can't follow 'normal' starting procedures as mine just won't fire up unless I hold the accelerator down (or pump it).
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  2. #2
    1000+ Posts silverexec's Avatar
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    I thought all carby cars had to be pumped (or have their accelerator held down) before they are started, to fill their bowl or whatever it is.

    I know in our carbied XF Falcon that standard operating procedure (according to the manual) is pump the accelerator a few times before starting the engine when it's cold. And if starting while the engine's hot, hold down the accelerator half way while starting it. The Falcon always seems to start instantly when following this procedure.

    Cheers,
    Richard
    - Richard

    Now: 405 SRI D70 '93
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  3. #3
    1000+ Posts Rod Hagen's Avatar
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    silverexec:
    I thought all carby cars had to be pumped (or have their accelerator held down) before they are started, to fill their bowl or whatever it is.

    I know in our carbied XF Falcon that standard operating procedure (according to the manual) is pump the accelerator a few times before starting the engine when it's cold. And if starting while the engine's hot, hold down the accelerator half way while starting it. The Falcon always seems to start instantly when following this procedure.

    Cheers,
    Richard
    Pumping actually empties the bowl, Richard (by squirting fuel out of it through the accelerator pump into the inlet manifold - until the engine is running it won't be replaced by a mechanical fuel pump). Essentially it gives a richer mixture than usual. Holding the pedal down without pumping weakens the mixture (by letting more air in through the throttle butterfly).

    Essentially pumping and holding have opposite effects. You hold down without pumping to overcome flooding. You pump to increase the amount of fuel getting into the inlet system. (but see below re auto choke cars)

    Most carby cars in theory require starting by pulling out the choke and then starting with your foot off the gas pedal when cold, and by having the choke off and thye pedal partly depressed when hot.

    However, in an auto choke car pumping the accelerator will also turn the choke off.

    If Nick is pumping the pedal for cold starting he may be effectively turning the auto choke off in the process , but compensating for this to some extent by pumping.

    What happens if you try using no pedal at all when cold starting, Nick? This should ensure that the auto choke is on (assuming its working properly).

    Possible explanations of the increase in idle speed could be - wrongly adjusted (high) idle speed setting coupled with non operation of the choke on start-up.

    Incorrectly adjusted fast idle setting

    Some bizarre set-up of linkages or vacuum lines.

    Which model Solex do you have?

    Cheers

    Rod
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  4. #4
    Guru davemcbean's Avatar
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    Rod Hagen:
    However, in an auto choke car pumping the accelerator will also turn the choke off.
    Not always. With the Auto choke Webers you need to pump the accelerator atleast once in order for the choke flaps to be able to close, because a limit stop prevents this from happening in the slow idle position.

    There are probably other auto choke carbies which also need a pump or two to engage the choke. I haven't had a close look at the Solex although I have a couple lying around if anyone wants me to check.

    Dave
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  5. #5
    Too many posts! JohnW's Avatar
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    davemcbean:
    Rod Hagen:
    However, in an auto choke car pumping the accelerator will also turn the choke off.
    Not always. With the Auto choke Webers you need to pump the accelerator atleast once in order for the choke flaps to be able to close, because a limit stop prevents this from happening in the slow idle position.

    There are probably other auto choke carbies which also need a pump or two to engage the choke. I haven't had a close look at the Solex although I have a couple lying around if anyone wants me to check.

    Dave
    R8/R10 Solex carbs have auto chokes. They need a single pump when fully cold, after which the strangler valve will be closed and the butterfly valve will be slightly open. You start with foot OFF the accelerator as the idle speed is high (that butterfly slightly open). Then those components gradually return to normal (hot running) positions as the engine warms up. They work pretty well actually - mine was 30 years old before it needed attention.

    With these carbs, when really hot, it is sometimes necessary to start with full throttle (to weaken the mixture) as the accelerator pump tube dribbles fuel down the throat and the result is too rich a mixture to start!

    This may be irrelevant to the Peugeot Solexes.

    There are few books on these Solex carbs, but I have two - a good web search will eventually turn them up.

    JohnW
    JohnW

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  6. #6
    Gone Fishin' Ray Bell's Avatar
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    The mechanical fuel pump is working whenever the engine is turning, one pump per two turns.

  7. #7
    nJm
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    I have a Solex 32-35 TMIMA or something like that.

    The instruction booklet actually says to not touch the accelerator when the car is cold, and to fully depress and hold it when starting a hot engine.

    What I find is that when it starts I need to accelerate up to 3000rpm (in neutral) as the engine doesn't rev cleanly. Then it idles fine, albiet at low revs.
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  8. #8
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    Revelation!!

    After months of poor cold starting, just ten minutes ago I started the 505 GR ( not used since Sunday evening ) with a Weber manual choke and it started first go.
    This time I pumped the pedal furiously about six times before turning the key and presto!

    ___________________________
    peugeot_ '83 505 GR

  9. #9
    nJm
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    That's what I usually do.
    Nick
    1983 Peugeot 505 GR


    "All of its cars from the 1.1 litre 205 through the ugly duckling 309 to the 2.2 litre 505 GTi had a rightness and a righteousness about them that turned every humdrum drive into a journey. Someone, I once wrote, in the bowels of Peugeot understands handling and how a chassis should feel." - Jeremy Clarkson

  10. #10
    1000+ Posts silverexec's Avatar
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    Rod Hagen:
    Pumping actually empties the bowl, Richard
    Well, shows how much I know about carbies... I learn something new each day.
    cheers!

    Richard
    - Richard

    Now: 405 SRI D70 '93
    - 2.0L manual
    Earlier: 505 GTi Executive '85
    - hence "Silver Exec"...
    25 GTX '86
    - manual conversion

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