No luck, still leaks with new (slightly thicker) fiber washer. But I took a very close look at the surface of the screws, they are not smooth, very slight gouges.
So I will try to get some new ones of those. I have some orings on them at the moment, but they aren't made for fuel. But they are working.
Has anybody used a better gaskets than fiber washers? They don't seem to dig in or cushion very much, there has to be better seals for when the surface isn't perfectly smooth?