Here's a systematic approach to troubleshooting:
1. Check the Wiring Harness: Carefully inspect the wiring harness between the fuel pump relay and the fuel pump itself. Look for:
* Broken Wires: Look for any frayed, broken, or corroded wires. Pay close attention to areas where the harness might bend or rub against other components.
* Loose Connections: Check all connectors along the harness. Wiggle them gently to see if the voltage fluctuates. Corrosion at the connector pins is a common culprit. Clean the connectors with a wire brush or contact cleaner if necessary.
* Ground Connection: A poor ground connection can also cause a voltage drop. Trace the ground wire from the fuel pump back to the chassis and ensure it's clean and firmly attached.
2. Measure Voltage Drop Along the Wire: This is crucial. Use a multimeter to measure the voltage at different points along the wire leading to the fuel pump. Start at the relay output, then measure halfway to the pump, and finally at the pump itself. The voltage should drop minimally along the wire. A significant drop between points indicates a problem in that section of the wire.
3. Inline Fuse (Less Likely, but Possible): While less common than a wiring issue, it's *possible* there's a fuse somewhere in the wire, particularly if there's an additional circuit branching off that wire for another fuel system component. The car's wiring diagram will be your best guide here – consult a shop manual or online resource specific to your 1995 Oldsmobile Cutlass Supreme.
4. Fuel Pump Inertia Switch: Some vehicles have an inertia switch that cuts power to the fuel pump in the event of a collision. Locate this switch (often under the dash or in the engine bay) and check if it's tripped. Reset it if necessary.
5. Fuel Pump itself (Less Likely): While less probable given your voltage readings, a failing fuel pump could draw excessive current, causing a voltage drop. However, this is less likely if you're getting any voltage at all.
Important Safety Note: Always disconnect the negative battery terminal before working with any electrical components in your vehicle. Fuel is flammable, so take appropriate precautions when working near the fuel tank.
If you can't find a problem in the wiring after carefully checking all of the above, then you may need to seek professional help from a mechanic or auto electrician. They have specialized tools and experience to diagnose more complex electrical issues. Providing them with your voltage measurements will be extremely helpful.
