priming diesel fuel systems

[Striven]

I been through a massive rollacoster, been through an awful lot that does not help me with stuff that I picked up and thus needing to brush up.

I was wondering if some of you could help me out when it comes down to bleeding diesel fuel systems starting from the basics to up and above.

Starting from the basics, scenario in both types with a lift pump and with out, I have just replaced the diesel fuel filter:

How do you know which pipe is the feed to the filter, the obvious aim being to fill the filter with fuel.

Second scenario is when the high pressure pump has been disturbed. (obviously you will bleed the high pressure pump from the low pressure return that probably loops back to the filter, it be better or safer to do it at the return at the filter.)

I kindly thank in help in advance.

[Jimmyarm]

Its pretty obvious which pipe is the return on most systems, just follow the leak off piping from the injectors back.