I was fueling my 1998 ML 320 when all of the sudden the gauge dropped to O even thought I filled my tank. What can be wrong is the gauge bad or a blown fuse?

The in tank fuel level sender on the ML is a pretty common failure, especially with a car as old as that. It is not too bad of a job for an experienced DIYer, but if you don't not have experience working with fuel systems, I would leave it to the professionals.

Thank you for answering. My husband is a very experienced mechanic, but not on on MB. Where can we look instructions on how to replace it?

Thank you

Remove the rear seat and pull up the carpet. There is an area that looks like the top of a paint can close to the hump on the left side. You need a large four fingered wrench or a huge channel lock to remove the screw on cap. Then use a fuel line tool to depress the two tabs on the lines and remove them from the pump/sender unit (all integrated). Replace the part and put it all back together. Make sure to use a good sealing compound to replace the paint can lid and get it on there straight (this is a safety issue).

Thank you.

Happy to help. Make sure you've got very good ventilation. The fumes fill up in the vehicle very quickly. I still remeber the headaches from my days on the line doing these.