What is the electrical wire for that goes to the Choke on my 1986 F-150 300? And if I unplugged it, how would my truck run? Lean or Rich? Thanks

 

the wire is what heats the spring and sets the choke. If you unplugged it your choke would cease to work.

 

Not trying to hijack, but a related question. My 85 has an electric choke, but the carb also has the place for the heat tube coming off the exhaust manifold. Do I need both, or is the electric choke all that is needed?

 

There are some guys on here who know exactly how this works, but the electric part is just a "assist" and I believe it has a thermostat inside that controls it. In other words in certain conditions the electric doesn't work. This is the stock Ford system. There are aftermarket systems that are all electric.

 

The stock Autolite 2100/4100 and Motorcraft 2150 carburetors never used a fully electric choke. The early Autolite 2100/4100 carburetors used a thermostatic "hot air" choke, and the later Motorcraft 2150 used a thermostatic "hot air" choke with "electric assist."

The way the thermostatic "hot air" choke works is this:

Clean, filtered air from the air cleaner is pulled through the "fresh air" tube (a rubber hose that is connected to the carburetor air horn and attaches to an aluminum tube) and into the bottom of the choke stove chamber on the exhaust manifold, where the air is heated up when the engine is running. From there, the heated air goes back up through the insulated "hot air" tube (attached on the top of the choke stove chamber on the exhaust manifold) that connects to the choke cap. As the air gets hot, it closes the spring in the choke cap, which allows the choke plate to open up as the engine warms up to run on a leaner mixture.

This is the idea on how the stock thermostatic choke stove was originally set up:




The "electric assist" portion of the stock choke system found on the later Motorcraft 2150 carburetor does not work on its own like an aftermarket electric choke. In fact, it doesn't have to work at all in order for the choke to be effective. It is only there to "assist" the hot air choke in temperatures above 60 degrees, where it helps the choke come off sooner for cleaner emissions. It doesn't work at all when the weather is colder than 60 degrees. It connects from the choke cap by a wire that connects to the back of the alternator. This part of the choke is secondary, meaning the choke will work fine without it, but the choke will not work without the thermostatic "hot air" choke system.

The thermostatic "hot air" chokes works MUCH BETTER than the fully electric chokes found on all aftermarket carburetors in that the choke opening corresponds with the engine temperature. As a result, the engine gets the right amount of choke it needs, and because it uses hot air generated from the engine, it doesn't choke the engine when it isn't needed.

 

That makes sense. I have the carter YF carb on mine, but I assume it all works the same.