The resistance board for the level aren't a part I'm aware of sold. They can be cleaned and the wiper can be bent to increase pressure to get those working.

When that fails the symptom will be the fuel gauge will not go to full. The runs out of gas at 1/4 tank is a very different problem. That happens when the o-ring seal on the "sending unit" fails.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)