Mechanical Switches (older vehicles):
* Simple Rotary Switch: This is the most basic type. It's a rotary switch with positions for each tank (e.g., "Left," "Right," "Both"). Internally, the switch is essentially a series of contacts. Rotating the switch connects the fuel lines from the selected tank(s) to the engine's fuel pump inlet while isolating the other tank(s). Think of it like a multi-position electrical switch, but for fuel lines. Gravity, or a low-pressure pump (sometimes called a lift pump) moves the fuel from the selected tank to the main fuel pump.
* Poppet Valve Switch: Some systems use a poppet valve mechanism within the switch. Rotating the switch moves a small valve that opens and closes the fuel passages to the different tanks.
Electrical Switches (more common in modern vehicles):
* Electrically Operated Valves: Modern systems often use electrically operated valves controlled by the selector switch. The switch itself sends a signal to an electronic control unit (ECU) which, in turn, activates solenoids that control the valves. These valves open and close the fuel lines to direct fuel from the selected tank. This allows for more precise control and can incorporate safety features like preventing switching tanks while the engine is running at high speeds or under specific conditions.
Regardless of the type (mechanical or electrical):
* Safety Features: Many fuel tank selector switches have safety features built in. For example, some prevent switching tanks while the engine is running to avoid potential fuel starvation issues.
* Indicator Lights: Usually an indicator lamp on the dashboard shows which tank is selected.
* Potential Failure Points: Mechanical switches can wear out over time or get stuck, while electrical systems can suffer from solenoid failure or wiring problems.
In summary, the fuel tank selector switch acts as a gatekeeper, selectively routing fuel from one or more tanks to the engine based on the driver's selection. The complexity of the system can vary greatly depending on the vehicle's age and design.
