Relays are real hard to test but they don't fail very often. What you might consider is popping the cover off the relay and reinstalling it that way, then you can squeeze the contact with your fingers. If you see a tiny spark when you release it, you'll know the wiring to the pump motor is okay. A helper can listen by the tank to see if the pump is running. You can also place a rubber band around the contact to hold it on.
You can also test the wiring at the relay socket but I'm not sure which relay style you have. Any chance you could post a picture of the socket? One terminal must have 12 volts all the time and one will read very low resistance to ground. That one is reading through the pump motor. I'm not sure about the two terminals for the coil in the relay. Most likely one will have 12 volts when the ignition switch is turned on or the other one will read to ground. I don't know which one is switched on and off.
You also might want to use a test light to check for voltage right on the gas tank when the relay is on. A common problem with steel tanks is a poor ground through the rusty gas tank straps. To fix that, drill a hole through the flange outside of the welded seam and run a self-tapping screw into it. Attach a new ground wire to that screw and attach the other end to a clean rust-free spot on the body.
Wednesday, April 27th, 2011 AT 7:26 AM