32 ADFA diaphragm problem

[mdj6248]

My son was rebuilding the carb on his (our) '78 Spider and he took apart something he probably shouldn't have and damaged a diaphragm inside it. The part is #42 on http://www.carburetorfactory.com/expvw36.html. I'm not completely certain what that is, but it has a small diaphragm in it similar to part #18 on the diagram. He damaged the diagram in taking it apart, and as far as I can tell that one isn't included in any standard rebuild kit and I haven't been able to find it listed as a part anywhere else. Any suggestions on how to deal with this?

[SoFlaFiat]

I'm from the school where, if you have it apart, replace all the stuff that rots or wears out. Diaphragms got old and part of rebuilding the carb is replacing those. I think you are right in that it isn't included it the general rebuild kit but you can get new diaphragms. I rebuilt my 32 a while back and if I remember... I got the diaphragms from C.Obert
Tell your son it needed to be replaced anyway and send him searching for the new one.

[manoa matt]

That diaphragm is for the fast idle electrovalve. The fast idle system prevents the carb from popping and sneezing on deceleration and going down hills. This kit from Italy has the diaphragm, it's the red one.


http://www.ebay.com/itm/WEBER-32-ADFA-3 ... 439e7d0cc5

[VermontMatt]

I'm pretty sure the Fiat part number for the diaphragm is 9928410

I just bought one here http://www.ebay.com/itm/FIAT-124-Spider ... 0908878918 but I don't see another for sale. I looked long and hard to find that one -- most of the rebuild kits I've seen don't include it. Try searching for "high idle diaphragm" or "fast idle diaphragm". I even saw one (for a different carb) listed as a "smog diaphragm", since the function of the fast idle system is to reduce NOX emissions.

[seabeelt]

I think Danny for Funipmorted.com has or had them. I got mine from him a while back when I was working on the 78
R/

[garion]

Hijacking thread slightly:

I don't have that part (42) at all, its completely missing on my carb. The hole that goes into the carb itself is 'open'.. Should I try and get ahold of that part, or is it ok without it (and plug the hole)? Also, I'm missing part 58, which I think pulls down on part 40, which is part of the vapor recycling stuff. How necessary is it? Could either of these be the cause of my 'sits for a week, have to wait for the fuel pump to get gas to the carb again' issue?

[VermontMatt]

garion, you don't need to replace that part. And in fact, you don't need to plug the hole, either.

Below is a page from a manual which describes the whole system. As you can see, the small hole into the carburetor body is an "air bleed passage". The way it works is this: when the system is sending vacuum to the vacuum capsule (the part you don't have), the vacuum pulls up on a diaphragm, which raises a small rod, which pulls up on the throttle linkage a little bit to keep the idle from dropping all the way down. When you no longer need that system to be engaged, the vacuum signal goes away -- but there has to be some way for air to re-enter the capsule, so the diaphragm can return to normal. That's what the air bleed passage does. It's just a small tunnel through the carb body from one hole which is open to the outside air to another one; it won't cause a vacuum leak if you leave it open.