fuel priming pump won't pump!

hi guys,

Put a new fuel filer on,   filled the filter with diesel.

Carefullly bolted her back in and clamped up the lines.

Loosened the bleed bolt.

Pushed the priming pump on the top down about 300 times.

No fuel at all.

Got a vacuum pump and sucked fuel up through the supply line from the tank and as clear as a bell. Not a speck of dirt.  Excellent easy flow.

Put it back together and refilled the filter cartridge.

Pushed the priming pump on the top down about 300 times.

No fuel at all.


Pulled the priming pump out and cleaned the little flap valve and seems to work well. Blew through the little gauze filter abd clean as.
Reassembled and still won't pump.

The pump appears to be faulty.

Any ideas?