carb help needed

[btoran]

My 1975 spider has had idling problems on-and-off since i got the car. at first it would stall, even after warmed up. So my garage adjusted the carb but then it idled too high, so i brought the car back and they set it lower. it was fine for a while but now it's idling too low right from a cold start. the other day, it refused to start at all unless i held the choke all the way open.

i checked the carb solenoid and with the ignition on and it seems ok. the relay opens and closes when i remove the power to the solenoid and put it back on.

i took the air filter off and noticed the hose that goes to the air filer has a cut in the end of it. you can see it in the right of this picture. i also noticed that there were no clamps holding this hose on.


on the air filter itself i also noticed a small tube sticking out from the main one at a 90 degree angle. you can see it in this picture.


my questions:
1. should there be a clamp holding the hose to the air filter?
2. should anything be connected to the smaller tube on the air filter? if so, what?
3. would simply cutting the hose where it is is split and reattaching it make a difference in the way the car idles?
4. is there a "fiat carb adjustment for dummies guide"? i'm handy and can turn a wrench and do electrical work, but i've never had a need to work on a carb before.
5. can i clean the carb without taking it off/apart?

thanks for your assistance.

[aj81spider]

Some answers based on my recent experience with my 74. In the event of differences between what I tell you and what someone who actually knows what they're talking about - believe them!

1. should there be a clamp holding the hose to the air filter?
There are no clamps on my 74.

2. should anything be connected to the smaller tube on the air filter? if so, what?
On my 74 there is a plastic line that goes to a nipple on the carburetor (a DMSA)

3. would simply cutting the hose where it is is split and reattaching it make a difference in the way the car idles?
That hose goes to the crank breather on the block. I don't think it will have any effect on idle.

4. is there a "fiat carb adjustment for dummies guide"? i'm handy and can turn a wrench and do electrical work, but i've never had a need to work on a carb before.
I would get Brad Artigue's Engine and Maintenance Manual. It has a pretty good section on adjusting the carbs.

5. can i clean the carb without taking it off/apart?
Can't help you here!

[westy64]

I would say there is no way of properly clean a carb without removing it.

on some others you can remove the jets and tubes and clean them with compressed air, but I do not see the jets on this one.
is the brass screw on the left side of your picture a filter retainer ?
maybe could you start there and clean it, and have a new inline fuel filter being installed, to prevent any trouble from the fuel.

then, you have to go from the up to the down I mean check the float level, the needle valve, etc...

without removing the carb, you can check if your barb has an air intake, by using a spray of brake cleaner around the basis of the carb, around the throttle axles, while the engine is at idle.
if the engine revs up, then you have an air intake in the area where you sprayed.
to be more precise, you can do the same with a small brush and fuel.

at least, I note that you removed the studs where the air filter is bolted.
did yo do this on purpose, or did they came when you tried to remove the nuts ?
I would think it is not good to make the theaded holes last...

good luck !

[btoran]

on closer inspection, i found a barb on the carb itself that is not attached to anything. it's on the front of the carb and faces the front of the car. you can see it in the right middle of this picture.


what, if anything is supposed to be connected to this barb?

is it supposed to be connected to the small barb underneath the air filter?

[131]

is it supposed to be connected to the small barb underneath the air filter?

Yes.

Inconsistent idle can be many things, crap in the idle jet, float level, worn needle valve, air leaks, worn throttle shafts. If checking for air leaks, use something a bit less volatile than fuel. Spraying WD40 or similar around gaskets in the base and the throttleshafts will momentarily stop air being sucked in and the idle will change, if it does you've found your leak.

[garion]

I followed the pic in the this thread to hook my 78 ADFA up:

http://www.fiatspider.com/f08/viewtopic.php?f=5&t=13517

[btoran]

Well, i bought some hose and connected the two barbs and she fired right up. Idle is still a little low. Will try to reset to factory specs per the artigues guide.

[majicwrench]

Very very few shops can fix carbs anymore. Gotta find some old guy. I know there is an old guy in the NW corner of MT who is pretty good with em

Number one issue with these carbs and idle is the idle jet getting plugged. ANYTHING can and will plug it.
With engine running, slowly lower hand over carb. Does idle improve?? If so, is too lean.
Remove idle soleniod, jet is in end. To properly clean it, you need to energize soleniod!! A jumper wire to the terminal, then hold soleniod to something metal, "clikc" it should open. Now blow compressed air or carb cleaner thru jet. Got glasses on?? Fire extinguisher?? Don't do this near fuel etc, you may create some tiny sparks. WHile soleniod out blow thru passage where solenoid goes, again carb cleaner compressed air. Reinstall soleniod. Do you know were ilde mix screw is at base of carb?? Set it about 2 turns from bottom to start. If you've got brads article is should explaiun setting idle mix.
Keith

[bradartigue]

Based on your pictures - y es, absolutely, an open port is an air leak and cause idling problems.

Here is what I would do with that carburetor:

- Clean it. It's filthy. Buy two or three cans of carburetor cleaner, put on some safety glasses, and clean the hell out of the outside of that thing. Scrub it with a toothbrush while cleaning. Spray everything you can get to (use the little hoses that come with the cans) and spray until it looks like it is new. Spray inside the barrels, too. Spray, spray, spray. If you look straight down at your carburetor you'll see two smallish (1/4" holes). Spray directly into them and you'll see fuel spray into the carb body. You'll spend 20 minutes doing this and spend $6.00; worth every penny. Let it sit for a while so the junk evaporates and then lightly spray some lubricant on the throttle assembly. Give it an hour or so if you sprayed a bunch cleaning the barrels as it will have flooded the cylinders (it evaporates rapidly though).

- Get some vacuum caps from Auto Zone, they are sold in little boxes and cap off any vacuum port that is not capped or connected. An uncapped port is an air leak and causes lousy idling.

You can tune follow procedures I have here: http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf which really are just a reproduction of a standard Weber tuning procedure.

If the idle is wavering, up and down "hovering" around but never settling at 850 then you have an air leak. It could be in the spacer between carb and manifold, they can crack. With the motor running you can spray lightly around with carb cleaner or wd-40 and you'll know when you find the leak because the idle speed will go up. If this happens near the carb base and a new spacer doesn't fix it then you probably have worn shafts and need a rebuild. I've found this to be uncommon except in the very cheap Webers (30DIC and) and hot rod Webers (30DGS), one because it's a cheap carb (DIC) and the other because of the owner's driving habits (DGS).

Good luck and reach out if you need help.

on closer inspection, i found a barb on the carb itself that is not attached to anything. it's on the front of the carb and faces the front of the car. you can see it in the right middle of this picture.


what, if anything is supposed to be connected to this barb?

is it supposed to be connected to the small barb underneath the air filter?

[btoran]

brad - thanks very much for your assistance. i will clean the system and check for additional leaks as you suggested. i also want to reset the carb to factory settings. i downloaded your carb guide but don't see a diagram of the 32adfa that shows me where the idle speed and idle mixture screws are located. i took the below picture looking straight down the carb. are the screws the ones the white arrows are pointed to? if so, which is which? if not, where are they located?

[majicwrench]

Those are not adj screws, they are air bleeds. Any manual will show you where idle speed screw is, but to steer you a bit it is on throttle linkage on firewall side of carb.
Idle mix screw is on carb base, pointing out towards drivers fender.

Cleaning outside of carb, in my not-always-humble-opinion is waste of carb cleaner, but knock yourself out if so inclined.
Keith

[westy64]

at least I can see that your filter is bolted to the carb with bolts, and not studs with nuts.

Is this normal, or has it been changed by a PO ?
And it seems that the bolts are very clean... are these stainless steel ?
If so, be careful with stainless steel close to carbs, as if one stainless steel part falls into the carb, you might have trouble to get it back, and you won't be able to use a magnet to take it back (ask how I know...)

[bradartigue]

On those nuts and bolts - I'd get rid of them. Threaded posts and nylox nuts are what should be there. But you're a ways from worrying about that, first thing you should do is take that air cleaner off so you can get to the carb and tune it.

As noted those "screws" you show are actually the air correctors, underneath those are the emulsion tubes. Leave them alone. They are hard as hell to get out of there anyway, I usually just pump carb cleaner down them.

On the clean carburetor - I like clean stuff. Clean stuff tends to be easier to work on. When I used to use a mechanic he wouldn't clean anything, his logic being that dirty FIAT engines don't leak because the crud is all that is holding them together. I stopped using him, I clean everything, and things tend to work. Probably doesn't matter...just a preference.

All of the Weber downdrafts are basically the same within their own series; you have an "A" carburetor and on that you'll find a mixture screw in the base, it usually has a spring around it and a knurled surface. To the right is the mechanical adjustment for the idle stop screw. The idle jets are above it on both sides. One of them has a solenoid and a wire running to it on many FIATs (some it does not), it is the one above the mixture screw; the other is between the cam tower and the carburetor.

Before you do any adjustment just get those open tubes blocked off and see how it runs. Then get into tuning it. You shouldn't have to do much more than set the idle stop screw and the mixture. This is all by feel, you turn the mixture screw very slowly until the motor either runs more smoothly or not. Find the spot where it runs best. A good running motor will not huff and puff (too lean) and will not blow black smoke (too rich). After you run it for a while you pull a spark plug and look at it, if it is black then you're a little rich, turn the screw IN. If it is white then you're a little too lean, turn it OUT. If it is brown you're in the sweet spot.

You can pull the idle jets and check the size of them, clean them up. I don't know what the size for an ADFA is off the top of my head, I think it is in my book, but you can find it easily online. They come out easily and you just remove them from their holder and spray carb cleaner through them. Spray it into the hole they came out of as well. Don't use a wire or anything to try to clean them (though a toothbrush bristle won't hurt, a wire will gouge the brass).

Tuning these things isn't rocket science and never let anyone tell you a Weber is hard to tune. You'll get it figured out the first time and then it's easy as can be.

[btoran]

Brad - thanks again. I ran a hose between the two barbs and the engine fires right up like it did before. It is idling too low so i'll clean everything like you suggested and then tweak the idle stop an idle mixture screws.

[btoran]

update......

she starts right up, idles perfectly, and runs better than ever. she purrs like a kitten and gives a subdued roar when i step on the gas, returning nicely to idle afterwards.

here's what i did:

unused barb's connected to each other.
split at end of main intake hose repaired.
carb cleaned (i didn't disassemble. just removed air filter and housing and gave it all a good spraying.)
idle mix screw adjusted.
idle speed screw adjusted.

thanks very much to everyone for your assistance!