Mercedes Gas tanks are inside between the trunk & back seat so no straps are involved these tanks wont rust out & leak. Like said before check the hoses coming out of the tank.

The Fuel Lines can look rusty for along time before they leak but they will spring a leak someday & the common place that Ive seen them leak is where its routed above the suspension arms (the big one connecting the 2 control arms). That is why I dont think its the greatest idea to jack up the car on the suspension arms or the differential because Ive seen it done & the leak that happened when that older somewhat rusty line got pinched then leaked.
If It is the line convert to rubber fuel lines as far as you need to get solid line.

My friend even had a leak so bad he couldnt get home but he had a roll of rubber fuel line so he dumped out the washer fluid & filled the washer tank full of diesel & routed the rubber line into the washer tank. A mess everywhere but hey you need to get home.