BRIGGS & STRATTON 3.5HP MOTOR STARTS BUT DIES?

Following up on Bob and Phil's suggestios:
1. Emptied fuel tank, cleaned and refilled with gas.
2. Removed carburetor, cleaned and blew fine mesh filter.
3. Replaced joint seal and diaphragm.
4. Engine starts and dies unless priming is maintained manually (tough)
Q. It seems fuel is not being pulled by diaphragm. Since diaphragm is actuated by engine vacuum could there be a leak? Where?
Rubber gasket seems to be OK.