Can a fuel pump be accessed through the back seats on a 1993 Crown Vic?

Yes
1st pull tire from pass rear. 2 tie exhaust to pass side to help clear fuel pump access cover. 3 remove fuel lines loosen passenger tank strap and gain extra wire length . 4 remove access cover 8 mm bolts and work module out of tank. 5 replace pump assembly and 6 replace parts as removed.

check the park neutral switch for proper operation

Definately sounds like the fuel pump

look under seat and u will ee the rails on each side of seat rock seat back and forth to locate wich bolt is loose or broken or if the rail itself is broken if rail broken remove the seat and order or go to a junkyard for the rail

99 crown vic pump is located in front side of gas tank right behind rearend, jack car up by frame to lower rearend out of the way to gain access to pump.

try changing the fuel pump relay...its on the driver side fuse box near the brake line

Nope. Fuel pump is located inside the tank. Some vehicles (don't think the CV's one of them) will have an access in the rear of the trunk to do this procedure. you can look insude the trunk near the back seat and if its thre you will see an access hole about 6-8inches around an that will allow you to pull the pump but only a hand full of car makers have this option. Its not very common

could be a bad fuel pump,check for pressure

check for clogged fuel filter first, usually the pump works or it dosen't, check and get back to me.

where is the fuel pump relay on a 2001 crown vic p71