accelerator pump issues

I'm having the exact same issue on my car. 72 Dart 225/Auto with 55k miles. No modifications, and everything at least looks stock and unmolested, just from looking.

I also read somewhere else that in older carbs, there's an o-ring on the acc. pump that newer ethanol-based gasoline can swell/distort.

I'll be using the tips here when I get a chance to look at mine closer.

Thanks!