1997 Chevy Silverado Fuel system

Do you hear the fuel pump for a few secs when you turn key to run?

CSI injection system the pressure should be 60-66psi

SFI injection " " " " " 56-62psi

Blocking the return line will cause the fuel pressure to increase-what's the reading unblocked?

Fuel Pressure Regulator Tests

This test checks the operation of the fuel pressure regulator to make sure it changes line pressure in response to changes in engine vacuum. This is necessary to maintain the proper operating pressure behind the injectors and to compensate for changes in engine load.

With the engine running, disconnect the vacuum hose from the pressure regulator. As a rule, fuel system pressure should increase 8 to 12 psi with the line disconnected. No change would indicate a faulty pressure regulator, or a leaky or plugged vacuum line.

Also, when the vacuum hose is disconnected from the regulator, check the inside of the hose for any wetness that would indicate fuel is being sucked into the hose. There should be none. If the inside of the hose is wet, it means the diaphragm inside the regulator is leaking. This will cause a drop in fuel pressure, and allow fuel to be sucked into the intake manifold upsetting the air/fuel mixture. If the diaphragm is leaking, replace the regulator

Also test the fuel pump relay