ZEUS+

Use two wrenches, one on filter and one on line fitting. You can also use an oil filter wrench. Sometimes I have a wrench on one end and use an air impact if really stubborn.

StratfordShark

I feel tantalisingly close to a solution here Zeus+, but I'm missing something simple.

If I can remove the fitting then I have a new filter that I can in theory screw onto the old fitting attached to the fuel pipe. But how do I get this old fitting out of the old filter in the first place, since I'm unable to shift the old fittings at the moment?

Forgive me if this sounds like a dumb question or if I've misunderstood.