I used your link, and read it.
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Any idea on what the fuel pump pressure should be on a TBI system? My book doesn’t say Squat about it.
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The TBI fuel pressure specification for small block Chevy’s is 9 – 13 PSI with the truck running.
The fuel pressure is tested by using fittings to “T” in a pressure gauge and must be tested with the engine RUNNING.
I don’t have a schematic for your truck but this is my best educated guess at where the wires go.
Orange wire, hot all the time.
Power supply from junction block
Red w\white, not hot.
To ALDL terminal
Black w\white, not hot.
ground
Red w\black, not hot, goes to Fuel Pump Fuse, didn’t expect it to come hot anyway.
Out to fuel pump. This wire should have power for at least two seconds when you first turn the key on. It should also have power when the engine is cranking. If it does not get power the relay is most likely bad.
Green w\white, hot Only with starter engaged and turning the engine over.
From ECM – controls the relay
The ECM controls the fuel pump relay.
There will only be power to the fuel pump for a few seconds when you first turn the key to the on position. If you are turning the key on then walking around the vehicle testing for voltage to the fuel pump circuit there will be no voltage and should not be power to the pump.
When the engine has oil pressure a redundant circuit supplies power to the fuel pump. This circuit goes through an oil pressure sensor/sender.
Once the engine is running the fuel pump should get power from the redundant circuit and not need the fuel pump relay to keep running.