fuel pump not running

Galant was shut off one evening and would not start the next day.Engine turns over at normal speed and we have spark.Fuel pump did not run.We bought a Haynes repair manual (great help with troubleshooting)followed all the steps and found that the pcm is not signalling the pump relay(which has been replaced)to turn on the pump.With a jumper in place of the relay the pump and engine run.The manual suggests that the pcm may be faulty. We're thinking there is a sensor because when the ignition switch is turned on the pump is supposed to runs for a couple seconds then shut off till the engine is started.The pressure regulator has no electrical wires,it simply opens to return excess fuel to the tank.Can you tell us if there is a sensor and where it is located?
Thanks
Larry