Please refer to posts 5 and 6 above. Are you sure the pump diaphragm is installed correctly as from your description, it in incorrect. Perhaps you just mis-spoke regarding diaphragm / gasket placement. The pump diaphragm is under the heavy cover retained by the large single screw. The regulator diaphragm in under the cover retained by (4) screws. If pump pressure is low or non-existent, the engine can still run with the choke closed a bit or with needle settings opened farther than normal but it won't run right.