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.Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.Your 460 engine should have a fuel pressure service port located on the injector rail, once you locate it install a fuel pressure gauge and monitor the fuel pressure, normal pressure should be right at 32 to 45 PSI. There is only one fuel pump and its in the tank, see if you can get me the pressure readings and we can work from there.
The smaller line is the fuel return line and there should be no pressure on it. The service port will look like a valve stem and it will likely have a black plastic cap on it. See the diagram in the link below.https://dl.dropboxusercontent.com/u/104923897/Service%20port%20Aug%2026.pdf
If you have a 1996 460 then it has to have this port. Send me the picture you have and Ill have a look.
The first picture you have sent is the fuel pressure regulator. The second picture is just the injector rail, the service port should be on the rail just behind the thermostat housing.
Yes disconnecting the line at the filter will allow fuel to come out but you can not measure the pressure this way. You really need to connect the gauge to the service port and it has to have one if its an 1996 460 engine. Please take a closer look. The port is built right on to the rail.