Hello I will help you with your question,
If you still have the hose off the canister the valve on top of the fuel tank is supposed to only allow gas vapor out but keep liquid fuel in. If you are overfilling the tank then you will get liquid fuel out the hose you disconnected.
So a two pronged approach to this, first when the pump turns off do not try to round up or add any more to the tank. If you are not doing this the tank needs to be lowered and the rollover valve on the tank replaced. In either case the canister needs to be replaced so the system can be closed.
Let me know how I can help you with this
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