The story:

1) 3 port fuel pump from a 74 l-jet relocated to the front of the car
2) Replaced all fuel lines and installed SS lines in car
3) Went to test the 1.8L engine in the car, pump worked and I was getting 30psi between the fuel rails
4) Dropped 1.8L engine, installed 2.0L engine (total time pump not used about 2 weeks)
5) Fuel pump now runs, but no fuel at the 1st rail

What I've done:
0) Put more gas in the tank (about 3 gallons)
1) Switched the wiring to the pump to see if it was running backwards (and back again). No pressure, no gas at the rails
2) Pulled the fuel filter, dumped 1/2 gallon of gas on the floor (so fuel tank sock not blocked) replaced the filter with another. No pressure, no gas at the rails

Any ideas? I guess the pump could have "gone bad", but what are the odds?

I was thinking I could disconnect the "S" line at the pump, disconnect the fuel line before the first rail and blow compressed air through it to make sure it's clear.

Try putting gas into the feed line (S?). I filled it on the rubber line right off the pump that goes into the firewall. I had this trouble too. Did that after scratching my head for a 1/2 hour trying to figure out why it wouldn't prime. That got it going. Hopefully that will do the trick. Sears sells fuel line clamps btw. Makes the job much easier.

Mixed up send and return lines to engine compartment? The pressure regulator will not work in reverse.

That's the first thing I would check.

However, its not that unusual for a 40yr old fuel pump to fail. We have experienced 3 port units which no longer move fuel even though the motor still runs.

Well it works. I ended up jumpering the pump so I could run it continuously and that cleared everything.

Thanks for everyone's input.