Oldsmobile 13500114 Fuel Pump Relay

Several electrical accessories in a vehicle, such as the fuel injection system, horns, starter, and fog lamps, use relays to transmit the electrical signal to the component. Relays have a control circuit and a power circuit, with the control circuit opening and closing the power circuit. Defective relays can cause components to not operate properly. Most relays are located in the engine compartment fuse/relay box and must be replaced as a unit if they are defective. ISO relays, which follow International Standards Organization standards, are commonly used in these vehicles. The terminals on ISO relays are numbered to indicate their circuit connections and functions. The control circuit terminals are usually 85 and 86, while the power circuit terminals are 30 and 87. Terminal 86 is connected to battery positive (B+) voltage and terminal 85 is connected to ground if the relay contains a diode. If the relay contains a resistor, terminals 85 and 86 can be connected in either direction with respect to B+ and ground. Terminal 30 is connected to the battery voltage source, while terminal 87 is connected to the ground side of the circuit. An ohmmeter can be used to check continuity through the relay control coil, and if there is infinite resistance in both directions, the relay should be replaced. The relay can also be tested by checking for continuity between the power circuit terminals and by using jumper wires to connect the relay to the battery. If the relay fails any of these tests, it should be replaced.