Trying to fix the automatic choke in my 77. When I align the choke cover index marks, the choke plate is not fully closed. Manual says it should be replaced if this is the case, I got a new NOS thermostatic spring thinking this would solve problem. Still, when I index the new thermostatic spring with the mark on choke housing its not even close to closing the choke plate. After I rotate the thermo spring about 35 degrees, puts enough tension on choke to close it. Seems I cant get the choke plate to fully open at operating temp. Grrr. Thoughts? Choke pull-off diaphragm?
BTW, Merry Christmas to everyone!
32 ADFA Automatic Choke Question
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Odoyle
- Posts: 440
- Joined: Mon Dec 01, 2014 10:06 pm
- Your car is a: 1983 Pinafarina Spider
- Location: CA
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18Fiatsandcounting
- Posts: 3798
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: 32 ADFA Automatic Choke Question
Pages 10, 11, and 12 in the following link will likely help:
http://www.njfiats.org/joomla/images/st ... rkbook.pdf
-Bryan
http://www.njfiats.org/joomla/images/st ... rkbook.pdf
-Bryan
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SteinOnkel
- Posts: 1000
- Joined: Tue Feb 19, 2019 9:31 pm
- Your car is a: 1978 124 Spider 1800
Re: 32 ADFA Automatic Choke Question
It shouldn't fully close when it's cold. How would the engine get enough air to run?
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Odoyle
- Posts: 440
- Joined: Mon Dec 01, 2014 10:06 pm
- Your car is a: 1983 Pinafarina Spider
- Location: CA
Re: 32 ADFA Automatic Choke Question
???????SteinOnkel wrote:It shouldn't fully close when it's cold. How would the engine get enough air to run?
"With index marks aligned and carburetor at room temperature of 77 degrees F, check that choke plate closes fully and remains closed when primary throttle is opened."
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18Fiatsandcounting
- Posts: 3798
- Joined: Fri Mar 15, 2019 11:23 pm
- Your car is a: 1969 and 1971 124 spiders
- Location: San Francisco Bay Area
Re: 32 ADFA Automatic Choke Question
The function of the "choke unloader" is to slightly pull open the choke plates when the engine is being cranked or has started, and it works by sensing the vacuum in the intake manifold. When the choke is working ideally, the choke unloader will move the choke plates ever so slightly, either more closed or more open, depending on whether the engine is faltering or off and running. If you engage the choke fully with the engine off, the choke plates can be all the way closed, but they should open slightly as soon as the engine cranks or fires. Assuming the choke unloader is working as it should. 
Many Weber carbs also have a mechanical feature to open the choke when the secondary throttle plate opens a significant amount, with the reasoning being that the engine needs more air at that point and a mostly closed choke plate would limit the air flow too much. Some Weber models don't have a choke plate on the secondary barrel, and that also solves the problem.
Hope all that makes sense.
-Bryan
Many Weber carbs also have a mechanical feature to open the choke when the secondary throttle plate opens a significant amount, with the reasoning being that the engine needs more air at that point and a mostly closed choke plate would limit the air flow too much. Some Weber models don't have a choke plate on the secondary barrel, and that also solves the problem.
Hope all that makes sense.
-Bryan