If the engine won't idle for 30 seconds on the fuel in the carburetor, fix that first. Then plumb the fuel line at the carb inlet into a 1 quart or larger catch container. A good pump should produce at least a pint of fuel in 30 seconds at idle speed. It should develop around 2 to 3 pounds of pressure, with the carb inlet line deadheaded into a gauge, and hold the pressure for a short time after the engine is shut down. It should also produce at least 10 inches of vacuum at the inlet side of the pump, and hold that reading for a short time after shutdown. That tests the condition of the diaphragm, and the inlet and outlet check valves. Failing any or all of these tests means the pump should be rebuilt or replaced.
Just about all local parts stores sell a combination vacuum/pressure gauge with an assortment of adapter fittings. Every shop needs one!
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