i suspect the most likly cause of this fault is a faulty
voltage regulator in the instrument cluster making the
gauge read wrong, the clusters can be dis-assembled in mk1
puntos, the guage unit can be bought separately from a
this is easy enought too replace, but you will need a 4mm and 3mm allen key too
do the job.
i cant see it being anything but this unless the fuel pump has recently been out
of the tank recently,
it is possible too bend the rod that the level float is conected too.
hope that helps.