oil pressure switch

1990 Full size 4WD Blazer w/5.7 liter engine. My problem is the fuel pump continues to run after I turn the ignition off! Initial problem was the engine would not start. Found bad fuel pump and blown ECMB 10amp fuse. Replaced above and checked fuel pump relay operation all seems good. Currently I turn the ignition on "Hear the fuel pump turn on for two seconds then turn off" start the engine and everything seems to work fine. The problem is when I turn the ignition off the fuel pump continues to run. I can hear it very easily. I have been disconnecting the positive battery lead to shut the pump down. Will a defective oil pressure switch cause this symptom? Also how do you replace it as there are no instructions in my Haynes repair manual.

I think this is a great forum hope the administrators keep up the good work! Thanks ahead for everyone's help!!

I dont belive the oil sending unit has anything to do with your fuel system, i'd check the wireing dirgram for sending units and relays that actavate the elect. fuel pump. Let me know what you did to fix the problem, when it comes to ya. Good Luck!