How do you know its fuel pump not working? Volts at plug?

Better not be voltage at the pump; that would be a fire hazard in a crash. You must check there for the first one second after turning on the ignition switch or when cranking the engine. Those are the only times voltage will be there.

Did you check for spark?

WARNING: Fuel system pressure must be released any time a fuel line is to be disconnected.

Connect fuel pressure gauge C-3292 and hose adapter C-4749 or equivalent to fuel rail service valve.
On 1984-85 models, start engine and observe pressure gauge. On 1986-88 models, using ATM tester C-4805, place ignition switch in Run position and depress ATM button to activate fuel pump. Gauge should indicate 51-55 psi pressure. If pressure is as specified, remove gauge and adapter from fuel rail.
If fuel pressure is below 51 psi, install tester between fuel filter hose and fuel line and start engine. If pressure is now within specifications, replace fuel filter. If pressure does not increase, gently squeeze fuel hose. If pressure now increases, replace pressure regulator. If fuel pressure still does not increase, either the fuel pump is defective or the filter sock is obstructed
If fuel pressure exceeds 55 psi, remove fuel return hose from pressure regulator end. Install suitable length of hose to pressure regulator and place open end of hose into a clean container. Start engine and recheck fuel pressure. If pressure is now within specifications, check fuel return line for restrictions. If fuel pressure is not as specified, replace fuel regulator.

There should be 12 volts at the fuel pump plug, not the sender plug. The fuel pump will run for 2 seconds until the engine cranks and starts. Then it will run constantly.

Roy