Chainsaw Repair

Yes when doing a pressure check you need to seal the impulse line, the intake port, the exhaust port, and spark plug hole.   I use about 10 to 12 psi and it should hold for 3 to 4 minutes.

If you have an air leak you will know it right away.     

If your pressure test checks ok then something is wrong with the carb.   Maybe the order of the diaphragm and gasket are backwards.   I have done it myself.   Same for the other side of the carb.   I would double check those.