EG9 K20A3 3/30/2012Check your grounds first. If they are ok, typically it is the sending unit:
View the Fuel Level Sending Units Wagons at http://www.bjsoffroad.com/
It is $45 and that includes the sending unit, o-ring and filter.
Installation is easy, there is an access hole under the rear seat. Installation instructions are available on the above link.