If You've got Rusty Fuel Issues...

Very difficult. I always fought my old Landcruiser. Rust goes right through filters. I had an inlet filter at the electric pump, an AC sediment bowl filter up at the carb, + the sintered metallic filter into the carb when running a carb which accepted one.

I drained and flushed it several times, loaded it with pepples at least 3x and sloshed them around to "scrub" the tank, and drained the fuel and let it sit, then drained off, leaving the rust in the bottom Never did get it completely clean. That was way before the internet, and if POR-15 existed, I did not know about it

Look that up and try it. They make several products, you want the one especially to coat fuel tanks