1977 Mg bgt petrol tank problem?

[Droob]

Hi, new to this forum which seems to be great! If anyone can help would be appreciated. Just bought my third gt and never had this problem before. Had about a quarter of a tank of petrol and all going fairly well apart from a bit of backfiring! Anyway going down a hill petrol gauge dropped to zero, warning light came on and I konked out. Once back on the level gauge went back up again and off I went. Any suggestions please?

[Droob]

Thanks for all ideas so far. I think the previous owner put a new tank in so aftermarket. Have woken to another problem this morning, petrol leaking out of fuel cap/filler hose (filled the tank after the "downhill" incident) - is this something to do with ventilation (non!). The filler cap doesn't seem to be a vented one, probably help to change it?