1997 Chevy Silverado V8 Four Wheel Drive Automatic 170000 miles
Truck won't start, pour fuel into throttle and truck will start and run, you can drive it, it runs good. Turn it off and try to immediately start it, it will start and run fine. Let it set a few minutes and it will not start and run unless you pour gas in. We have 80Lbs. Pressure with return line blocked. What are we looking for?
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