My Chilton says the fuel pressure for a 4.9L @ 1995 is 40-50 psi, but for all other years before 1995 is 45-55 psi. I know Chilton is not the best thing to look up, but I don't have any other source now. Is this typo or what?
I had fuel pressure of a bit less than 40 psi @ idle. I changed the fuel pump. I get only 41-42 psi @ idle now. I didn't do a test under load yet. I am not sure if this is normal or not... My fuel pressure regulator is about one year old, so I thought the regulator was OK, but since the pump is now new, maybe the regulator is not working right (no leak, no gas smell from vacuum line though).
At idle pull the vacuum line to the regulator then check (and plug it), don't check with it, it will drop the pressure down to broaden the range of the integrator/O2 counts/injector pulse widths to keep them centered on spec. Just makes it easier to manage emissions.
I seem to remember my 91 at 38 at idle (regulated) and 45 unregulated.
With my previous fuel pump, with or without that vacuum line connected to the fuel pressure regulator, the pressure was same, about 38 psi or so (used to be 40-41 @ idle). After replaced it with a new one, I haven't tried it yet. Well, maybe my old pump was in a good condition... I may have to try to think of it as a preventive maintenance, oh well.