Here is the inside of a fuel pump that wouldn't pump after a few hundred miles. Can you tell from looking at it why it wouldn't work? Of course not. Short of a torn diaphragm or a missing or loose valve, opening up the fuel pump won't answer many questions.

The only way to test a fuel pump is to record the fuel pressure at the carburetor and the output.

The one with the silver top was brand new and wouldn't pump a drop straight out of the box. The problem with this Chinese garbage seems to be in the position and/or throw of the pump arm.

The silver topped one didn't pump a drop straight out of the box.

Yours looks like a reman of an original pump since it has the glass bowl but who knows? You can't really trust new parts to work properly anymore. I'd test the pump.
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1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)