Looks like I did have the gasket and diaphragm reversed, though fixing that didn't make a difference in the "manual pump" test (and that was after re-assembling it a few times, so it was probably correct to begin with). I then got carb cleaner and sprayed every open hole (after dis-assembling, including removing the welch plug (a first for me). Just put the engine back into the plane and - after five pumps - VOILA!! FUEL up to the carb! Too late to start it tonight, so am bringing with me to the field in the morning. Will let you know. (I'm going to have to re-tune, I'm sure.)