How do you diagnose no fuel pressure in 1989 XLT after replacing tank fuel pump and filter but not getting sufficient pressure at the injector rack?

I would make sure that the pump is running all the time. Is it getting current?Try a jumper wire to the pump; Splice it into the positive lead .There are two wires at least to it and a separate for the gauge. I went through this whole thing to find out I had a frayed wire near the pump. I hope this helps you. Mark

try the pump on the frame there are 2 pumps high & low low is in tank

Answer:

Also check the interia switch. It may need reset. It is located on the passenger floor board, under the carpet next to the tranny hump.