Needle valve is a globe valve with a conical plug (needle) closing into a small seat. Used for flow metering and damping pressure fluctuations on instruments such as pressure gauges... Instrument isolating valves are often called needle valves.
Most car engine carburetor has needle valve that controls the precise flow of gas on the float bowl. Controlling enough gas flow will ensure proper function of the car engine’s carburetor. If the float bowl has too much gas, it may flood the carburetor making it malfunction. On the other hand, having too little gas may also damage the carburetor not allowing it to start at all. Checking your carburetor to see if all parts are intact and functioning on its desired performance should be done every now and then. Checking your carburetor can be easy and only requires little technical experience from the person doing it.
Carburetors installed on your engine uses needle valves in the float to either stop the flow of fuel or add fuel to the float bowl. The needle valve flow control allows the carburetor to maintain the required amount of gas on the float bowl. As soon as gas runs out of the float bowl, the float moves down going to the needle valve. This motion will create an opening that will allow gas to fill the float bowl. Once gas has filled the float bowl to its required amount, the float rises and the needle will cut off the flow of gas. Once the carburetor runs out of gas, and the float bowl did not function as it should, the engine will not function as well. It can either have a hard time starting or it will totally not start at all.
In a nutshell, you can do this by checking opening your carburetor. You need to find the float needle valve screwed on the top portion of the carburetor’s body. This valve is controlled by the float as it moves up and down as required amount of gas is needed; when the float bowl is full of gas, the float moves up closing the needle valve. This motion will stop the flow of gasoline in the float bowl. So, when this action is being impeded by dirt or deposits formed in any part of the carburetor, it can make the engine unable to start or stop it in the middle of the drive.
A needle valve is a type of valve that is designed to control the volume of liquid that flows in small lines. As the liquid that passes through the valve makes ninety degrees turn passing through an orifice that seats a rod with a cone-shaped tip, the size of the orifice changes depending on how much or how little liquid flow is required.