On V6 cars with A/C the sender is here:
On non-A/C cars the sensor is screwed directly into the block, just above the filter:
Note, this is the '88 sender, it looks slightly different than the previous years but is still in the same location. Do not use a big socket to engage the hex at the top of the sender, that will destroy it. Use the proper size wrench on the fitting next to where it screws into the adapter. Use an adjustable wrench to grip the block that the sender screws into, otherwise you will crack the tube.
To test if the sender is indeed defective, at least as far as the fuel pump circuit goes, just unplug it. If the pump stops, then the sender is bad. The cause of this type of failure is actually a failed fuel pump relay, oddly enough. When the relay fails the parallel circuit in the oil pressure sender will provide power to the fuel pump after a few moments of cranking to get the oil pressure up to trigger level. Since the sender isn't designed to do this duty full time the contacts eventually fail, usually by welding themselves closed.
[This message has been edited by JazzMan (edited 01-15-2004).]