Fuel tank breathing system (Fuel delivery system)

Fuel tank breathing system

1. Filler neck breather pipe
2. Filler cap
3. Cut – off valve
4. Two – way valve
5. Fuel tank
6. Charcoal canister
7. Purge control valve

Fuel tank breathing system operation

During filling, air trapped in the fuel tank by the rising fuel level is allowed to vent to the top of the filler neck by a separate breather pipe.

When sealed by the filler cap, fuel tank breathing is via a cut – off valve, which prevents liquid fuel from entering the breather system, and a two – way valve which allows expanding fumes to exit the tank. From the two – way valve, fumes are directed to the charcoal canister, where they can be purged into the engine via the purge control valve.