fuel pump pressure; 450 sel

Can anyone help? I have a 1980 450 sel (gas), it sat for a couple of years, fuel is bad. I cannot get enough pressure to the injectors to open them. I have 40 psi
to the distribution system, fuel to the injectors, but assumedly not enough to open them. I had 2 of the injectors tested to see if they were clogged ... they were not. The pump does work. Is it possible for it to work but not under enough pressure? Is the correct pressure 70 - 80 psi? Can the filter be bypassed to see if it is clogged. I did remove the pump and filter unit, and ran varsol though it to clean it out, yet to date I have not tried it back in the vehicle. Any ideas out there?
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