Stalls at Stops

[Franksplace2]

This problem began not long ago. As I approach a stop, I shift to neutral and the rpm drops t0 10k rpm. Then as I stop the engine stalls. It restarts without a problem. Maybe the air flow is interrupted for some reason. I tried to increase idle speed but was unable to increase it.

Thanks for any insight.

Frank
1979 Spyder
2 barrel carb

[seabeelt]

Check for vacuum leaks

[TX82FIAT]

After you check for vacuum leaks check your voltage when the car is on and when the car is off.

[Exit98]

This is a carb car right?

There is a idle solenoid on the carb with a wire connected to it. Disconnect the wire and clean and tighten it. With the wire off turn the key on. Touch the wire to the solenoid, you should hear it click. The car won't idle without this functioning.

[majicwrench]

Voltage doesn't have anything to do with it.

I'm always for trying the simple things first. Just don't ever stop and see if that works.

[DanD]

This is a carb car right?

There is a idle solenoid on the carb with a wire connected to it. Disconnect the wire and clean and tighten it. With the wire off turn the key on. Touch the wire to the solenoid, you should hear it click. The car won't idle without this functioning.

It also won't idle if the jet at the end of the solenoid is clogged.

[bradartigue]

You say "2 barrel carb" - which one is it? ADHA (stock) or something else?

Need to know in order to diagnose; the stock carb on that model Spider (CS2) has a few things that can cause the carburetor to stop delivering fuel on decel. Not being able to increase idle is a symptom of some of these things.

[Franksplace2]

Check for vacuum leaks

No vacuum leaks found

[Franksplace2]

This is a carb car right?

There is a idle solenoid on the carb with a wire connected to it. Disconnect the wire and clean and tighten it. With the wire off turn the key on. Touch the wire to the solenoid, you should hear it click. The car won't idle without this functioning.

There is a gold spade connector on the left side of the carb. It does not click. The idle is very rough whether the connector is on off.

[Franksplace2]

You say "2 barrel carb" - which one is it? ADHA (stock) or something else?

Need to know in order to diagnose; the stock carb on that model Spider (CS2) has a few things that can cause the carburetor to stop delivering fuel on decel. Not being able to increase idle is a symptom of some of these things.

This is a weber carb made in Italy. On the right hand side of the carb is a lever with a screw adjustment. The lever seems to be the adle adjustment. It was initially set midway with a round locking ring. The screw ends in a point slot on the carb. Initially the point was loose. I loosen the round locking ring and was able to advance the screw to the max. The point was still loose.

It is possible to post pic or docs here?

Thanks for your help.

Frank

[bradartigue]

Open this document:

http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf

And read section 4.8, then tell me what carburetor you have. Which Weber is it?

You can read the whole thing if you like, but for now the important thing is to tell us what it is so we can help. All the Webers are a little different, and the stock carb on the 79/80 was very different.

[GeorgeT]

10K rpms is a lot! Maybe you meant 1K (1000). Anyway, mine would do the same and the problem was that the alternator had a bad diode and was not generating enough current (volts) to both run the motor and the brake lights, one or the other but not both. Replaced the alternator and all was well.

[Franksplace2]

Open this document:

http://www.artigue.com/fiatcontent/Arti ... 124_MM.pdf

And read section 4.8, then tell me what carburetor you have. Which Weber is it?

You can read the whole thing if you like, but for now the important thing is to tell us what it is so we can help. All the Webers are a little different, and the stock carb on the 79/80 was very different.

I read section 4.8 carefully and spent a hour searching for the carb id number. The lowest section has 4 flat faces but no numbers anywhere. I jacked up the car and searched for the engine ID with no success.
I found Weber carbs on http://www.artigue.com/. The ADF looks like mine. The face (towards the fender) bottom section has the adj screw and two holes which are jumpered. The mid section has a damper and accommodates the spade connection. The right face (firewall) bottom section connects to the linkage. The middle section has a dome with 2 hose connections. I did not find a pic of the of the ADHA. Can we go forward with the ADF?

[TX82FIAT]

I know the carb set up is different and suspect it is a fuel related issue. However, i had a 79 that stalled at stops. As George T pointed out with his alternator Diode problem. On the 79 back in the 80's the alternator Voltage regulator had issues and the car would not cycle and adjust RPM's to voltage requirment. When I stopped at a stop light it would stall. Never could really figure out how it was able to hold enough juice in the battery with a failing regulator. In any case, a rebuilt alternator did the trick. I would not buy or rebuild an alternator until testing the voltage. I know some on here said voltage would not cause a stall at a stop. Maybe it was just my car many years ago. I have a $3.00 cigarette lighter voltage meter that I plug in that helps me see how the voltage and voltage regulator are adjsting to RPM's. 13.8 volts at idle and 14.4 volts if higher RPM. 12.4 volts when just off the battery. Something as simple as a lose V belt could cause issues.

[bradartigue]

The issue is if you have an ADHA the diagnostic is different, it is an odd carburetor.

Send a picture of the thing to me, I can ID them by sight - brad <at> artigue <dot> com

One thing that isn't different though is how you set the idle speed. Some ADHAs have the mixture screw capped off, none of the ADFs have it capped, so follow the procedure either in my book or FIAT's (they are roughly the same) and get the basic mixture and idle speed setting correct. If you cannot set the idle using the procedure then something else is wrong; report back.