1987 GMC C1500 engine

Over the past 6 years I have had a problem with the electric fuel pump not coming on when I turn the ignition switch on. I replaced the fuel pump 4 years ago and the problem still persist. It happens maybe two or three times a year. It can be 70 degrees above zero or 20 degrees below zero. Sometimes It would come out of it by disconnecting the battery and then reconnecting it or leaving it be for a period of time. Sometimes change in temperature would also cause it to start working again. The last time it quite working was a year and a half ago. I have tried disconnecting the battery, banging on the fuel tank, moving wires and tapping on the steering column nothing works. Its -20 and now when I need it to plow my road out it won't work. Help!