I recently had a fuel pump problem with my 91 740. Mine is a Belgium Volvo and has the Regina system with one pump. First I would check the relay, take it out and jumper back to the relay box. Then, take the relay cover off and turn the ignition to start. You should see and hear the relay actuate. If it doesn't, you need to replace it. If it does work, time to check the pump. I have never seen a base model 91 740 with the Bosch system(with two pumps), so I can't help there. Two ways to tell the difference, check the ignition coil on the driver's side strut well, if it is square and looks like a transformer, then you have a Regina system. The other way is to look underneath the car, under the driver's seat. There should be a brace/shield with fuel lines running to it. Underneath this should be a big fuel filter(Regina) or a smaller filter and pump (Bosch). If you have the Regina system with one pump, the pump could simply be clogged or the filter sock on it's suction clogged. If the sock is clogged the pump has no NPSH and therefore will not actuate, because it will create a vacuum. The pump could be clogged also, by trash or gunk. I simply removed the pump and sending unit, wired the pump up straight to the battery and ran it(AFTER THE FUMES AND GAS EVAPORATED). The pump would not run, I wired it in reverse, removed the sock, and ran it, viola, worked perfect. I ran it for about 30 seconds in reverse, rewired it forward and operated, worked fine. I wouldn't run the pump dry for more than 30-45 seconds, it could damage it. These pumps are tough though and should outlive your engine. The cool thing about the Volvo is the access port in the boot, just pull up the boot liner, and the port is on the driver's side. You have to be very careful, gas fumes are abundant,don't spark, and have plenty of ventilation. Removal of the pump is straight forward, just take your time. Also, don't cut any hoses unless you have replacements.
Hope this helps,
G.W. (I love run-on sentences and improper structure about as much as I love Volvos)