My fuel pump primes constantly instead of the normal 2 seconds it supposed to take, the engine only cranks and doesn't fire. when I leave the key in ignition on while the pump is priming I can here a hiss in the engine bay near the fuel line. If I press the pin on the schrader valve gas does squirt out so the pump is delivering gas. Does anyone know what the problem is and why the engine doesn't want to start?