heres the soution to this problem
the fuel guage in the tank is a float type
it falls off itsmounting bracket quite easily i found when mine did this
all i had to do ti fix this is to open the fuel tank from the boot ant reposition the guage
heres how to fix this
but before you do this its an idea to have an almost empty tank of fuel and to remove the battery completely to avoid sparks as you will be opening the fuel tank
step1: unscrew metal plate in boot on right hand side beside the strut tower
step2 : unclip all wires leading into fueal tank but leave hoses attached (no need to remove them)
step3 : unscrew the big plastic cap on the fuel tank be sure not to drop the rubber sealing ring into tank (plastic cap may need some gentle ppressure to move)
step 3 : reach into bottom of fuel tank and fing your guage
step 4 : just down and a little to the right of the fuel tank opening on the front wall is where the bracket is
bend the clip the guage sits on a little to ensure it dosent fall off again
step 5 :make sure all wires are atached to guage and clip into place and also make syre you cant unclip it ( i used some large zip ties to secure inplace to make sure it dosent come off again)
step 6 : close fuel tank re attatch all wires and put cover plate back on make sure tank is sealed and that you can no longer smell fuel vapours in the boot before re installing the battery.
step 7 : stat her up and go to the servo fill up about 20 - 30 litres and make sure guage works
all should be good now
DISCLAIMER : !!!!
i only recommend tat people who are profesional mechanics or who love to exploe themselves and their car to do this job
you will inhale a lot of fuel vapours doing this and the smallest spark will blow you and your car up so be carefull