Fuel pump relay location 1990 chevy subburn

One of the easiest ways is to listen for pump to cycle in tank "HUM" when someone cycles key to on. If you hear "Hum" pump is getting power. The other would be to swap it out with another in that area, with same # on it. Under hood, passenger side, on firewall usually. Should be at least one more relay there with same #. There are so many ways that manufacturers recommend for different vehicles, this is usually the easiest. If I can't test for power in & out of relay when key on, I'll go direct to tank sender & check for power there to be sure.