If you are sure it is just some sort of gunk that will desolve in gas then just blow it through with compressed air.
If it is something more substantial like a piece of rubber fuel hose, it will not desolve and will just block the line.
You can also take off the brass banjo fitting on top and use a piece of rigid or semi-rigid wire to "rotor-router" the line.
You can see how the tube goes almost to the bottom of the tank in the picture John posted.
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