Diagnose Fuel Delivery System Failure

What happens here

The host begins to troubleshoot the engine's inability to start by investigating the fuel system. He attempts to open the drain plug of the Zenith carburetor but finds no fuel flow. He suspects ethanol fuel contamination. He then checks the glass fuel filter bowl on the opposite side of the engine, confirming fuel flows from the tank to the filter, but not past it. He drains the old, murky fuel from the filter bowl, discovering a missing filter element and confirming a significant blockage or issue within the fuel filter or the line leading to the carburetor.

Goal: Identify the exact point of fuel system blockage preventing engine start