Question- carb

[BigOrsnge]

Want is the circled part and what does it do? Just got a new carb, just trying to figure it all out. Not really a place for it.

 

[ared77]

This help? -

Carburetor throttle solenoids and idle stop solenoids are used to reduce idle RPM to prevent engine run-on when ignition key is turned off. They also were used to increase idle RPM when the A/C was turned on to prevent stalling. Dash pots slowed the closure rate when throttle was released quickly.

 

[BigOrsnge]

So, I guess my question is- do I need it? It didn't seem to be doing anything on the previous carb. There's really no way that I see it would work with the new carb (nowhere to connect bracket). There's no A/C on my Bronco either. Or, guess I can fire it up and see if it diesels after I shut it off.

 

[ared77]

Yeah, you really don't have to use it. I believe they were an add on during the early "emission years" in the automotive world.

 

[DirtDonk]

Did you happen to keep the old carburetor? You can always rebuild it, or have it rebuilt, to use at a later date.
But no, you probably not need the idle solenoid. I think it’s a great idea, but isn’t absolutely necessary. And most carburetors don’t come with a way to install it easily.
Did you replace it with another stock carburetor, or an aftermarket?

 

[BigOrsnge]

Did you happen to keep the old carburetor? You can always rebuild it, or have it rebuilt, to use at a later date.
But no, you probably not need the idle solenoid. I think it’s a great idea, but isn’t absolutely necessary. And most carburetors don’t come with a way to install it easily.
Did you replace it with another stock carburetor, or an aftermarket?

Still have the old carb. It was a cheap piece of crap I put on it just to get it running again. Replaced with a Holley 350. I basically just replaced everything involving fuel delivery etc. from tank to lines, pump, and carb. Been having a fuel flow issue and it was time.

 

[Broncobowsher]

I see a wire on that solenoid. Is it connected to anything?

Back in the 70's the emissions controls were very crude. One of the things that was done was to retard the timing and turn up the idle screw to keep the engine running. This would idle at a lower manifold vacuum, which was also a higher cylinder pressure. The higher cylinder pressure got a better burn and reduced emissions. The problem was engines didn't want to stop running. A few hot spots in the engine and higher cylinder pressures and the engine would run like a model airplane engine, dieseling. To get the engine to stop when the ignition was turned off they put on the solenoid. The solenoid would be what held the engine at idle speed. Key off and the solenoid would drop the throttle more closed. To the point there just wasn't enough air (and fuel) going into the engine for it to run.

From the sounds of what has been done, you no longer have stock emissions equipment and the engine is running a non-emission profile. You don't need the solenoid at this point. Even if the wire is still hooked up the function has probably been bypassed several carburators ago.

Sometimes they were also used as a kicker with old A/C compressors. When a massive compressor would bog an engine down at idle this would give it a kick to keep the idle up.
People have installed them for other reasons. When you want a fast idle. Little extra engine cooling. Maybe a better charge out of the alternator when winching or just giving a jump start.

 

[BigOrsnge]

I see a wire on that solenoid. Is it connected to anything?

Back in the 70's the emissions controls were very crude. One of the things that was done was to retard the timing and turn up the idle screw to keep the engine running. This would idle at a lower manifold vacuum, which was also a higher cylinder pressure. The higher cylinder pressure got a better burn and reduced emissions. The problem was engines didn't want to stop running. A few hot spots in the engine and higher cylinder pressures and the engine would run like a model airplane engine, dieseling. To get the engine to stop when the ignition was turned off they put on the solenoid. The solenoid would be what held the engine at idle speed. Key off and the solenoid would drop the throttle more closed. To the point there just wasn't enough air (and fuel) going into the engine for it to run.

From the sounds of what has been done, you no longer have stock emissions equipment and the engine is running a non-emission profile. You don't need the solenoid at this point. Even if the wire is still hooked up the function has probably been bypassed several carburators ago.

Sometimes they were also used as a kicker with old A/C compressors. When a massive compressor would bog an engine down at idle this would give it a kick to keep the idle up.
People have installed them for other reasons. When you want a fast idle. Little extra engine cooling. Maybe a better charge out of the alternator when winching or just giving a jump start.

The Solenoid wasn't working. Never did a thing (since I've been fooling with it). As for emissions, there's not even so much as a muffler been on it in decades (straight pipes out of headers). No Canister. No A/C ever on it. Been in my family since 1977.