If it running down the block by the lift pump..... ensure the filter drain is closed, check the main steel line from the lift pump to filter also..... at the filter end there is a rubber seal under the cap nut on the line.... see my gallery
Air/fuel leak points.....
http://www.intellidog.com/dieselmann/filter.jpg
Air/fuel leak points.....
http://www.intellidog.com/dieselmann/filter.jpg