If you unscrew the knurled wheel enough it will contact the lower Schrader valve (tire valve) and allow air into the filter. If this does not work then use the one on the filter header to allow air in to drain fuel
If you go
www.intellidog.com/dieselmann/filter.jpg to this page you will see all the parts of the filter.
I first drain the water separator on the bottom by unscrewing the knurled wheel and collecting about 1/2 cup of fuel from the steel drain line in a plastic container. Close drain and remove the WIF light connector and the drain line hose from the filter. Using a filter wrench unscrew the filter from the head, trying not to spill the remaining contents. Look inside to see if any water or crud has passed through the filter system. Now drain the filter then remove the filter base and clean it.
Assembling the new filter, place the new slightly oiled oring in the separator base groove, screw base and filter together hand tight. Fill the filter with clean diesel or fuel additive via the outer small holes until 1 inch below the top, lubricate the upper filter seal and screw the filter to the header. Hand tighten first then 1/2 to 1 turn more with a filter wrench is required. Now retighten the base by hand slightly if required. Install WIF connector and drain hose.
With a helper, purge the air from the filter by pressing on the valve stem in the schrader valve (use a rag to catch fuel) while starting the engine. Wipe up any spills jobs done. Note stumbling may occur until all air is removed from the system.
Bleed air from the Schrader valve, engine should start when fuel is present.
