Fuel can't flow to connected tanks through interstages. All parts have fuel line on but the blue tanks don't send the fuel to the engine.
@AndrewGarrison it doesn't always work, I couldn't find the cause, the xml seemed to be right (the engine showed the tanks as connected) and the fuel didn't flow, just dettached and attached them again and it worked
Just enable the Fuel Line on parts 5 and 6 as well.
@AndrewGarrison it doesn't always work, I couldn't find the cause, the xml seemed to be right (the engine showed the tanks as connected) and the fuel didn't flow, just dettached and attached them again and it worked