<VV> Sputtering

[Richard]

Everything was fine with my 66 Monza for a while until yesterday when on a short trip to town it started sputtering when I floored it (power glide transmission) . When I backed off the g as pedal it ran and idled OK.  I removed the fuel pump and it seemed ok.  I blew air into the fuel line and it bubbled into the gas tank.  I'm ready to order a new fuel pump, but I was told that because it is a diaphragm pump, it's either good or not good...nothing in between.  Is that true? Maybe it's just carburetor s?

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