with all the preflight check, start up check blahblah checks, I am really doing a whole bunch of things which I don't currently understand. i would call up my instructor but he's probably drunk (that's a whole different story

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With so many instructors in here, I couldn't think of a better place to ask!
I understand vaguely why I have to do certain items on the check list, but I feel that I am lacking a cohesive understanding on how the whole fuel system work on the 152. (i.e. test-drain the fuel to see if there are any sediments and water since it's gravity fed, prime the engine on cold starts etc)
I really want to know how fuel travels from the tank (i know it's gravity fed, but what's next? reservoir? carburetor?), how it gets into the engine? where does the fuel gauge measure from? why do i have to prime on cold starts? etc
does anyone mind taking me through the end to end process of the fuel system on a 152? I have tried googling this but haven't found anything useful
thanks in advance!
E