Chevrolet Astro Forum : “How do I relieve the fuel system pressure when changing the fuel filter?”

There should be a bicycle-type valve located near the intake manifold or injector rail where the fuel line enters the fuel injector system.  Put a rag over this and gently press in on the center of this Schrader valve and the fuel will spray out and get soaked up by your rag.  Do not start the vehicle again until the fuel filter is replaced as even turning the key on will pressurize the fuel system again.