* Wiring Diagram: This is the best and safest approach. A factory service manual for your specific year and model Lumina will have a wiring diagram showing the fuel pump circuit. It will clearly identify the power (positive) wire.
* Visual Inspection (Less Reliable): Look closely at the harness connector. Sometimes a thicker gauge wire is the positive, carrying more current. This is not always the case, though. Look for a fuse in the circuit; the wire leading from the fuse to the pump is likely positive.
* Testing with a Multimeter (Safest Method if you have the knowledge): This requires a multimeter capable of measuring DC voltage.
1. Disconnect the battery's negative terminal. This is crucial for safety.
2. Turn the ignition key to the "ON" position. This will energize the fuel pump circuit (usually for a few seconds).
3. Use your multimeter to test the voltage at the fuel pump harness connector. Set your multimeter to measure DC voltage (usually indicated by a "V" with a "-" symbol). With one probe connected to a good ground (unpainted metal on the car body, for example), touch the other probe to each wire in the connector.
4. The wire showing a voltage reading (typically between 10-14 volts) when the ignition is "ON" is the positive wire.
5. Important: If you get a reading only when cranking the engine, that's still the positive. The pump may only activate once the engine is being turned over.
Warnings:
* Fuel is flammable. Take extreme caution when working near the fuel tank and fuel system. Work in a well-ventilated area and avoid sparks.
* Always disconnect the negative battery terminal before working on any electrical system. This prevents accidental shorts and protects you from electrical shocks.
* If you are unsure about any step, consult a qualified mechanic. Improperly handling car electrical systems can lead to damage or injury.
Using a multimeter is the safest and most reliable method if you have experience with electrical systems and understand how to use a multimeter. If not, a wiring diagram or professional help is highly recommended.
