What component has a pinion gear that meshes with the engine flywheel?

The component that features a pinion gear that meshes with the engine flywheel is the starter. The starter's primary function is to initiate the engine's operation, which is crucial for starting the vehicle. When the ignition is turned on, the starter motor engages and the pinion gear extends to mesh with the teeth on the flywheel. This meshing action allows the starter motor to turn the flywheel, which in turn rotates the engine's crankshaft, facilitating the engine's start-up process.

The starter is specifically designed to handle the high torque required to overcome the engine's inertia, making it uniquely suited for this task. This function differentiates it from the other components listed, such as the alternator, rotary pump, and power steering pump, which do not engage directly with the flywheel or serve to start the engine.