Daryl,
My tank is rusty too. For a simple, fast, and temporary fix:
- drain your tank
- remove the fuel sender form the tank through the trunk (buy new cork gasket)
- disconnect fuel "breather" lines in trunk
- disconnect fuel line to electric fuel pump
- remove tank (3 bolts)
- remove filter screen from bottom of tank (buy new screen)
This gives you an access hole on each side of the tank. I simply used a garden hose with a hand spray nozzle to blast off as much rust as I could from the inside of the tank. I sprayed it back in where the holes where fuel drains to the electric fuel pump. I also sprayed it through the false bottom around the filter screen hole. I followed up by rinsing with fuel repeatedly and then letting it dry overnight.
To make the process more permanant, take it to a radiator shop to have them boil it out. This ensures all loose rust is gone. Also, use a POR-13 product or other similar sealant, or have a professional seal it. This is not a simple tank, of course, because of the double layer bottom and interior pipes running from the filter screen to the fuel pump. Take this into consideration when sealing.
Best of luck!
Rodd
1966 230SL Euro
1994 E420