Lift Pumps, 300 HPDI TXRC

[lockhah1]

Gents - Just purchased 2 brand new Yamaha OEM lift pumps to replace the ones in my motor. Out of curiosity, I tested them using my Mityvac (pressure/vacuum hand pump) per the service manual. There were no leaks across the diaphragm (as expected) but I was surprised the check valve(s) did not hold pressure/vacuum in the corresponding direction. Do the pump need to get wet for the checks to perform as specified?

[lockhah1]

Posting for future reference/info. The checks do hold pressure/vacuum per design once wet in gas.