1997 GMC K1500 4x4 5.7 ex.cab SFI injection system?

fuel pump died replaced it truck ran poorly afterwards. Had a prussuer test done pump determend pump was no good. Put in another ran good for 2 days started running poorly hard to start no power. 2nd fuel pump. So i figure another bad new fuel pump wow changed it put in a third brand new fuel pump. Still will not eve start now. I had it tuned up 2 months ago new plugs rotor, cap, etc. put in a new fuel filter made sure it is on proper checked all connections for leaks. this cannot be a fuel pump problem now. no problem with the elctrical i figure i have great spark on ignition tester. I can hear the fuel pump prime when i turn the key. but when i went and checked the fuel port i had no pressure. When it is being cranked gas sews out of the test port. Also i dont if this is comon cause i used to turn my keyand go. but when i have someone turn the key and i listen at the gas tank whn the key is shut off i hear gs spraying back into the gas tank. So i am open for opinions.