Method and system for adjusting pressure in a fuel tank

1. A vehicle system, comprising:

an engine;

at least two fuel vapor storage canisters fluidically coupled in series;

a first conduit coupling a canister purge valve to a first of the at least two fuel vapor storage canisters;

a first bypass passage coupling a vent port of a first of the at least two fuel vapor storage canisters to a low pressure port of a venturi pump; and

a second conduit coupling a first motive fluid port of the venturi pump and a load port of the first of the at least two fuel vapor storage canisters.

2. The vehicle system of claim 1 , further comprising a second bypass passage for a second of the at least two fuel vapor storage canisters and a third bypass passage for a third of the at least two fuel vapor storage canisters.

3. The vehicle system of claim 2 , further comprising a first bypass valve positioned along the first bypass passage, a second bypass valve positioned along the second bypass passage, and a third bypass valve positioned along the third bypass passage.

4. The vehicle system of claim 3 , further comprising a canister vent valve coupled to the third of the at least two fuel vapor storage canisters via a third conduit.

5. The vehicle system of claim 4 , further comprising a fuel tank isolation valve coupled to a second motive fluid port of the venturi pump via a fourth conduit.

6. The vehicle system of claim 5 , further comprising a fifth conduit coupling the fuel tank isolation valve and a fill limit vent valve.

7. The vehicle system of claim 6 , further comprising a canister purge valve and a controller including executable instructions stored in non-transitory memory that cause the controller to open the canister purge valve and the fuel tank isolation valve to activate the venturi pump.

8. A method for operating an evaporative emissions system of a vehicle, comprising:

reducing pressure in a fuel tank via opening a fuel tank isolation valve and opening a bypass valve of a first carbon filled canister;

flowing air and fuel vapors through a venturi pump; and

flowing the air and fuel vapors through a first carbon filled canister, the bypass valve of the first carbon filled canister configured to bypass the first carbon filled canister.

9. The method of claim 8 , further comprising opening a bypass valve of a second carbon filled canister to reduce pressure in the fuel tank.

10. The method of claim 9 , further comprising opening a bypass valve of a third carbon filled canister to reduce pressure in the fuel tank.

11. The method of claim 10 , where the pressure in the fuel tank is reduced in response to the pressure in the fuel tank exceeding a threshold pressure.

12. The method of claim 8 , further comprising closing the fuel tank isolation valve and the bypass valve of the first carbon filled canister in response to pressure in the fuel tank being less than a threshold pressure.

13. The method of claim 8 , further comprising reducing the pressure in the fuel tank via opening a canister purge valve.

14. A method for operating an evaporative emissions system of a vehicle, comprising:

mixing air with fuel vapors flowing directly from a fuel tank via a venturi pump during purging of fuel vapors from the fuel tank.

15. The method of claim 14 , where the mixing of air is in response to detecting a fuel slug is being delivered to an engine, and where the fuel vapors flow from the fuel tank without passing through a carbon filled canister.

16. The method of claim 14 , further comprising opening all bypass valves of the carbon filled canisters via a controller so that air may be delivered to the venturi pump.

17. The method of claim 16 , further comprising opening a canister vent valve via the controller so that air may be delivered to the venturi pump.

18. The method of claim 17 , where the venturi pump draws in the air and mixes the air with fuel vapors from the fuel tank.