Choke Thermostat
With few exceptions all combustion engines have a carburetor or one or more throttle bodies. The older domestic vehicles have carburetors. The newer models have throttle bodies to blend the air and fuel just like the carburetor does on older vehicles. Nowadays, the throttle body eliminates the need for a float bowl, etc. Both the throttle body and the carburetor need a choke which is one of the working components on your fuel system. The inventor of the carburetor was Karl Benz, who patented his invention in 1886. In the late 1980s carburetors were replaced by the modern fuel injection throttle bodies.
A choke thermostat is an integral and necessary component of the choke on the carburetor on older vehicles. On a newer vehicles today it is on the throttle body. The choke thermostat has a bimetallic wire or coil that is needed to assist choke operation. When the bimetallic wire on the choke thermostat heats up or cools down it will open or close the butterfly slightly so that the correct mixture of fuel an air is accomplished to start and run the vehicle.
An automatic choke on modern day cars can either be a divorced choke or an integral choke. If it is a divorced choke it will be located outside the carburetor on the manifold. The integral choke is one that is an integral part of the throttle body. The divorced choke has an operating rod that goes from the choke to the carburetor. The integral choke has a piston inside the choke housing. When the bimetallic coil gets hot it will relax and pull the choke open on a divorced choke. The integral choke needs a vacuum that is applied to the piston to open it.
When the choke thermostat fails it can cause the engine to have trouble starting. It will also cause engine stall upon acceleration when the engine is cold. When the engine is hot a failed choke thermostat can cause black smoke to come from the exhaust, poor fuel economy and even failure to pass the smog test. You can easily replace the choke thermostat on domestic cars and trucks. You can find choke conversion kits on various websites that can be installed on older vehicles.
When the choke butterfly opens up in response to the choke thermostat’s bimetallic coil it will cause the extra fuel that is needed for smooth operation. It will also adjust for smooth operations at low engine temperatures. The heat from the engine is transferred from the choke thermostat by convection. If an electric choke is being used it will have a sensor that will vary the electrical current that acts on the bimetallic coil. The bimetallic coil is connected to the choke or butterfly which will open and close.
When you are replacing the choke thermostat be sure to compare the old and the new one so that you get the correct one. There are various websites that sell replacement auto parts. You can also find a choke thermostat at your local auto parts store. If they do not have the correct replacement part that you need they can order if for you. You can also go online and order a new choke thermostat for your make and model engine as well. If you are not sure which replacement part is correct it is best to get advice from an experienced auto parts salesperson. When shopping for a new choke thermostat you can save money by purchasing one online. Many auto part websites offer discount auto parts. If your vehicle has fuel injection throttle bodies you may want to have a qualified mechanic replace the choke throttle for you rather than doing it yourself.
