What must you do with manual primer pump knobs to inject fuel into the cylinder?

To inject fuel into the cylinder using manual primer pump knobs, the correct action is to pull them out and then push them back in. This process allows fuel to be drawn from the fuel tank and into the engine's carburetor or fuel system. By pulling the knobs out, you create a vacuum that facilitates the flow of fuel. Once you push them back in, the fuel is injected into the cylinder, preparing the engine for starting.

This method is essential for ensuring that adequate fuel reaches the engine, especially during cold starts or when the engine has not been run for a period of time. Understanding this mechanism helps in effectively preparing your engine for operation and avoiding issues related to insufficient fuel delivery.