My bmw 320d is refusing to start

Don't worry I'm sure you will get the solution of your problem, just check the link I attach
https://www.reliable-store.com/products/2001-bmw-320d-330d-e46-car-service-manual-spanish

thermostat is stuck. change it
also check the viscous fan

If pump is bad it will

I'm guessing that you got an air lock in your fuel system as a result of your changing the fuel filter... I certainly don't know about a BMW diesel, but in most semi-truck engines, there is a priming pump just for the purpose of getting the air out ... and the fuel into.... the fuel system. I've even been known to fill the filters with diesel fuel before screwing them onto the base.. This is risky because of the possibility of allowing some foreign, unfiltered debris to get into your pump and/or injectors, just because of your putting unfiltered fuel into your filter... Check and see if there is some kind of priming pump close to the filter. Also, a possibility is that you may have an electric fuel pump.... as to where all you may need to do is loosen a fuel fitting on the pressure side of the pump and filter.... and allow the electric pump to purge the system of air.. I confess to my lack of knowledge on your BMW.... but, I do have some basic understanding of most diesel systems... Good luck..

I'd get a compression check done...

You probably fouled the sparkplugs. Change those and see if it starts ok.

ive just discovered this same problem with my bmw 320d this morning! any theories why it wouldnt lock? would be very helpful

Maybe this guide can help you like a reference guide: Change Air Filter (with pics).

I hope help you (remember rated this help). Good luck.

maybe air leak some where