Fuel tanks over flowing

You have the a vent on tank with a tube. Caps are also vented. On top should see a small circle. That’s the vent. It will seal off if tank gets pressurized, instead of leak.

 

If not a blocked line, or a line that was disturbed and routed differently. Might be the Gt splitter Return valve.

 

Turn the other 1 on

 

If draw tube in tank is blocked it won't draw from that tank but will still return fuel just the same to point it will overflow. Same if fuel line collapses internally. Also if splitter valve that controls return fuel is screwed it will return all to one side. Will o erflow slower that way generally but will overfill just the same.

 

I have had that problem. The fuel return line was blocked . Have had shut off valves installed. Can do the same with a pair of vice grips. Just put tape on the jaws