A diagnostic fuel storage system is provided and includes a pressure sensor configured to monitor pressure at one or more diagnostic points within the system. In accordance with one embodiment of the present invention, a diagnostic fuel storage system is provided comprising at least one storage tank, a filter system, at least one pump, and at least one pressure sensor. The storage tank includes a fuel vapor vent port. The filter system comprises a filter input port coupled to the fuel vapor vent port. The pump is positioned to cause fuel vapor to pass through the filter input port. The storage tank, the filter system, and the pump are arranged such that the storage tank and selected fuel vapor ducts in communication with the storage tank operate below atmospheric pressure. The pressure sensor is configured to monitor pressure at one or more diagnostic points within the storage tank, the selected fuel vapor ducts, and combinations thereof. In this manner, the pressure sensor is operative to provide an indication of operation above atmospheric pressure. According to another embodiment of the present invention, a diagnostic fuel storage system is provided comprising a plurality of fuel storage systems, a central data processor, and a communications link coupling the central data processor to each of the fuel storage systems. The central data processor is configured to process pressure data sensed by the pressure sensors.