mystery choke adj screw????

[puddin]

i have an 1800 with a weber 32 adfa carb-- there is a small flat head adj screw by the choke that is on a 3 post mount and i have not found what it does or how it affects the choke-- i rebuilt the carb and took it apart it seems to be a worm gear on the choke spring. i guess it's for take up slack or spring tension.... i'm not talking about the 3 screw hold down to adj the choke but on the adjacent side from the choke. aparently there is fuel or vac because there is an o ring seal for something ........ anybody wanna touch this one?????

[rasouth]

If I'm understanding you right, the screw you are talking about is on the upper side of the water choke housing, (two hoses attached). This screw is to adjust the position of the choke plate that is inside of the carb. When the engine is cold and needs the choke the choke plate should be at a slight angle. This screw holds the plate at an angle by resting on a notched plate and as the engine warms up the screw allows the choke plate to decrease its angle until no more choke is needed.
There is another screw directly under the choke housing that controls the idle speed and another screw towards the middle of the base that is for the mixture.

[puddin]

you got the wrong screw -- just above the idle speed adj screw is a flat head adj screw on the choke housing-- i don't get any response from turning this screw all the way in or out with the thottle open and cold. i use the 3 hold down screws and turn the housing -- i did notice two alignment marks on each side of the housing and thought they were merely suggestive-- i set the choke (cold) about 1/8 inch from being fully closed.. is this about right or not.. i live in MD and it's getting down to the 30's and the choke is needed to get me going in the morning commute....

what's the proper adj for the choke == anybody know

[So Cal Mark]

it sounds like you're asking about the fast idle speed screw. To adjust the choke closing, the housing has to be turned. The rule of thumb is that the choke plate should be lightly closed at 70 degrees F

[puddin]

ok -- did i mention that i'm POLISH

once again for clarity
1. this "mystery screw" is a fast idle speed screw???
2.then what is the long flat head screw on the throttle linkage than runs off the choke cam for? i thought that was for adj the fast idle since it rides on the "steps" ???
3. i guess this mystery screw utilizes some vaccum since there is an o ring on it and seems to be pushing pulling on an diagham
4. if it's freezing cold 30 degrees should the choke plate be nearly closed ?? would it make a difference by how fast the choke opens...

thanks
mark

[majicwrench]

http://www.carburetorfactory.com/expvw36.html

Now, what screw is it??

[puddin]

now that is what i needed gotta love the internet
#13 "the mystery screw"

just wondering how does this screw adj fast idle speed-- vac port????

[majicwrench]

Not fast idle screw. That is choke pulloff adj screw.

[puddin]

how does it effect the choke -- choke limit adjustment or closing rate maybe spring tension-- i think i'll just leave it fully seated closed

[majicwrench]

All carbs have some sort of spec for this adjustment.
THe choke plate should fully shut cold. When engine starts choke plate then needs to pull open slightly to keep engine from flooding. THe choke pull-off accomplishes this. It is a vacuum operated diaphram. The amount it opens the choke is adjusted by the screw in question. If screw is all the way in diaphram will just barely be able to open choke plate. With screw all the way out choke plate will open quite a ways.

[puddin]

you are magic== thanks so much for clearing this up -- i'll ge to work on dialing this in

[manoa matt]

The adjustment is a bit more involved than that. The only mention of the adjustment for that screw is in the 32 ADFA workshop manual which is a supplement to the Service manual. There is a special gauge that needs to be inserted into the choke housing to make the adjustment.

The diaphragms do not come in the carb rebuild kits, however I've seen them on ebay from time to time. I've rebuilt at least 10 of these carbs and never replaced the diaphragm or adjusted the screw and the cars run fine without it. There are however several other adjustments for the choke unloader that should be checked and performed when rebuilding and adjusting the carbs.

Send me an email for a copy of the 32ADFA workshop manual. It covers every adjustment and specification for the carbs.

matt.scarton@gmail.com

[majicwrench]

I was making no attempt to describe the proper way to adjust pull-off, simply telling him what the screw did.
Keith

Matt's cars probably do run fine without adjusting the screw. WHo needs a choke out there??

If you are operating the car in cool weather, adjusting screw will be critical to making car run properly first few minutes.

[manoa matt]

If the diaphragm does not come in the rebuild kits, and the vast majority of owners do not know how to adjust the screw or what it does as there is no mention of it in any of the 4 commonly available manuals, then how are all the Fiats with a 32 ADFA carbs even working properly?

Puddin's 2nd response: "I don't get any response from turning this screw all the way in or out with the thottle open and cold"

The main and important adjustments for the choke is the stepped fast idle cam minimum and maximum openings and indexing of the choke housing marks.

Here is the diaphragm for a 2000 series 28 ADHA carb which is very similar to the 32 ADFA http://cgi.ebay.com/ebaymotors/FIAT-WEB ... _500wt_956

[majicwrench]

Not sure what your point it Matt. Screw is there for a reason, if carb did not need it Weber not put it there. ALL carbs have some feature to adjust choke pull-off. Engine will operate better after initial start-up with screw properly adjusted.