260E W124 petrol Fuel tank ??

[Duner]

Left drivers side over the half shaft there are 2 lines exiting the fuel tank. One may be the fuel tank vent valve as it is cylinder shaped white plastic. The other has a 90 degree rubber molded line exiting the tank and attaches to hard line. What does this line do? My 90 molded is damp and if I replace it will I have to empty the tank first? Should I try to source a 90 degree molded or will a rubber fuel line work. Than you>