Replacing Diesel Filter


This should have been a straight forward job, but low and behold...

I take off the old filter and take out the sensor at the bottom. Drain the old filter. Fit the sensor to the base of the new filter apply a little lubrication to the seal on the top of the filter and start to screw it on. I turn it as far as it will go and then apply a little pressure to tighten. There is however still a small gap between the filter and filter holder. No problem me thinks the seal must have taken as the it will not turn any more.

I then go to loosen the air screw andf start pumping the filter to fill it. I pump and pump and pump and pump and pump but still no fuel appearing thru the air drain screw. I have checked the diaphram of the pump and that seems fine. So why wont the filter fill.

I bought the filter thru one of the recommended parts suppliers on this website

Please help. Like i said it hsould have been a straightforward job