Carburetor set up ADHA

[LarryM]

Hoping the carburetor gurus will chime in!

1976 Spider all original, one owner (my brother). Hasn’t been used much in years. Probably driven to the garage to get inspected & home each year for the last 10 or more years.

I believe it is has an ADHA Carburetor with different accelerator cable linkage than what shows in the diagrams I can find. That leads to some questions below.
I’m having trouble setting up the original carburetor after cleaning & rebuild. I rebuilt it because it was running poorly to begin with.
It has new gas
Here is the process I followed by Brad Artigue, after rebuilding the carburetor. Installed all new rubber hoses also & new plastic fuel filter while I was at it.

Preliminary Settings Note: These is the recommended procedure per Weber with some modifications, you will find the same general steps in any publication on setting up carburetors. Do not rely on the factory settings unless otherwise directed by your vendor
Back out the idle speed screw (A) in my photo) until it is no longer in contact with the throttle stop lever. Now turn the screw until it contacts the lever and again 1 ½ turns. DONE, did have to tighten it a little more.

Turn the idle mixture screw (B) in my photo) in until it is fully seated - do not force the screw. Now turn it back out two full turns. DONE

Disengage or block the choke open. On automatic chokes you can use a small clamp or wire to pull the choke mechanism open. DONE

The engine should start and run poorly (if it does not then increase the idle speed screw (A) ½ turn until it does). Adjust the idle speed screw until the engine runs at approximately 900 RPM. It does start and runs poorly. I adjusted to 900 rpm. Seems to be running very rich

Turn the mixture screw (B) in (lean the mixture). If the engine increases in speed then continue to turn until it is no longer increasing or runs worse, then back the screw out ½ turn. If the engine decreases in speed then turn the screw out until it is increasing in speed. Continue to turn until it is no longer increasing or runs worse, then turn the screw in ½ turn. Had to turn the idle screw in all the way to slightly improve the rich condition. Then I backed it out ½ turn. Seems something isn’t working in the idle circuit??
Adjust the idle to approximately 850 RPM. Let the engine warm up to operational temperature. On a Spider you will wait until the fan has cycled two times (on-off-on-off). DONE, note: should the engine fan come on during these steps STOP working until it shuts off. Set the idle speed screw so that the engine runs at 850 RPM, or 900 RPM DONE, still seems very rich and I can’t lean it out. if you have air conditioning. Recheck the mixture screw by turning slightly in then out. Engine speed should be set - using the mixture screw ONLY - to the fastest and smoothest point of operation (listen for exhaust popping). Reset the idle speed screw as necessary.

So here are my questions:
What do you do with the vac hose (which comes off the carb and would normally plug into the bottom of the air cleaner) during this process? Pinch it off?

Does the fact that the breather hose isn’t connected anywhere (since the air cleaner is removed) make any difference?

I have an idle cut off solenoid. If I disconnect the single wire to it, it makes no apparent difference. If I check the wire, it has battery voltage. Could this be defective?? Can I test it?

What are the other screws identified as C & D in my photos? They are the screws from the different linkage I don’t see in the drawings. They also seem to affect the idle speed.


Sorry, having problems loading photos right now.

[18Fiatsandcounting]

A few thoughts:

1) A '76 should have a 32 ADFA carb, so that might be why the diagrams don't match. If you do by chance have an ADHA, that carb was used in 1979 or 1980 and is a complete disaster. Get rid of it.

2) In general, it doesn't matter a whole lot if the breather tube and the thinner vent tube is connected while setting the idle. I typically get the carb set up with the air cleaner off, then do minor tweaking of the idle mixture screw with the air cleaner back on and the tubes connected.

3) Unless you have a feel for what 850 rpm sounds like or you know your tach is accurate, use an external tach. Fiat tachs can be considerably off at low idle speeds.

4) Turn the ignition on but don't start the engine. Disconnect and reconnect the wire to the idle stop solenoid. You should hear it click. If you don't, the solenoid is bad. You already verified that it was getting +12V when the ignition is on.

5) My guess is that the idle solenoid is bad, or something else is plugged up in the circuit, so you are "idling" by opening the throttle valve slightly so that the main jets start coming on. This will lead to a very lousy idle that will be impossible to adjust. And it will run rich. A bad idle stop solenoid is fairly common.

-Bryan

[LarryM]

Thanks Bryan,

Thought I hard a faint click the first time but nothing after that no matter how many times I un-plugged it & re-connected it. I assume it's shot??

Larry

[18Fiatsandcounting]

I assume it's shot??

Likely, but I would take it out and see if you can clean it up a bit. Perhaps it's just gunked up. New ones are not that expensive, but make sure you get the right size. The threads are either 8mm or 10mm depending on which carb you have.

If you have a digital multimeter, put it in the ohms range and measure between the connection and ground. I'm guessing it should measure between roughly 50 and 100 ohms. If it's zero or infinite, it's probably bad.

-Bryan