What sort of pump do you have?
On carburettors it usual to have a pump that only creates a few PSI. The flow of air pulls fuel from the float chamber. The fuel level in the float chamber is controlled by a valve which is closed when the float rises. Too much pressure will push the valve open and push the float down slightly.
Carburettors are normally fed by pumps that slow down or reduce their stroke when their maximum pressure is reached.
Something like this:-
https://www.mgbits.com/contents/en-uk/p8020_Fuel-Pump-(New-S.U.).html is what I would suggest. Some cars had two of those to get a large enough fuel flow.
Pumps like that are diaphragm pumps, where the diaphragm is pulled back by a solenoid to suck the fuel into the pump. When the diaphragm is fully back, the solenoid is turned off and the diaphragm is pushed by a spring to push the fuel into the carburettor(s). When the float chambers are full, the float valves close so no fuel flows, and the spring movement is stopped by the pressure of the fuel, so the pump just stalls.
In an old car that I drove that was like that, when the ignition was turned on, the fuel pump could be heard to click rapidly a few times and then slow and stop as the float chamber filled up. During running, the click rate of the fuel pump varied as more or less fuel was used.
Modern engines have fuel injection of one sort or another, and they use higher pressures. On those it's common to have a pressure relief valve so the fuel pressure can't get too high, and the excess fuel goes back to the tank. That also helps to keep the fuel in the engine bay cool, and lets air in the fuel system be taken back to the tank.