Fuel system in my training 152
It starts with 13 gallons in each wing, with fuel pipes that run from each tank down the door posts behind front seats, over to an on/off valve between the seats, from there it runs to a strainer in the engine compartment where it's filtered thru a screen, from there to the carburetor where it fills the float bowl, it will stay in float bowl until it is drawn out thru the idle jet, for idle or the main jet for partial to full throttle. This will happen when the pistons are on the downward stroke causing a sucking force, helped by the curved restriction in the carb called a venturi to draw atomized fuel/air up thru the intake manifold into the cylinders.
The primer works by drawing fuel out of the strainer and forcing it into the intake manifold directly behind the intake valve, however stock 152's only had one pipe from the strainer to one cylinder, so in some cases when you over prime, you will flood this cylinder, and the 3 others have no fuel for starting. The reason you need the primer is cos during cold starting crank the engine needs a richer mix and lower temps are not good for atomizing fuel, plus their isn't enough sucking by the engine to get extra fuel from the main jet.
You can start in very cold temps by, setting throttle to 1/2 inch, mixture rich, pull primer to fill chamber, then crank with right hand while pushing primer with left hand, the harder you push primer the better the atomization to aid the start, do this as required, once it starts, don't be in a hurry to in and lock the primer if it's out, let it stabilize first or you could flood it.
The fuel quantity indicators, are float type in each tank, as the fuel is consumed the float descends with the fuel level, changing resistance in the circuit and the quantity on the gauges