800s are prone to fuel leaks where the main fuel line is sited under the rear, nearside wheel arch. There's a nice little "protective" cover over the join which only serves to hold water and grot IN not out!
They can also rust out the filler neck, right up at the top. Again, you can see/feel this in the rear wheel arch area.
Otherwise, I'd be looking at all the fuel line joints, just as I would on any other car.