2001 Chevy Express it

I have a no start issue on a 2001 chevy van , the fuel pressure shows 62-64 pounds with it running and with the key on it shows 45-47 pounds , with the key off it shows 0 pounds , If I hit take the air filter out and shoot some 2+2 in the air cleaner it will fire up and run perfectly until I shut it down , then I have to hit it with the 2+2 again to fire it up , there are no trouble codes in the computer and I have good fire at the plugs , any idea where to go next ?