* Fuel Pump Relay Stuck Closed: The relay is an electrically-operated switch that activates the fuel pump. If the relay is malfunctioning and stuck in the "closed" position, it will constantly supply power to the pump. This is the most common cause.
* Inertia Switch Triggered (if equipped): Some vehicles have an inertia switch that cuts power to the fuel pump in a collision to prevent fuel leaks. If this switch has been accidentally triggered or is faulty, it might be preventing the normal shut-off signal. Check your owner's manual for its location.
* Faulty PCM (Powertrain Control Module): The PCM is the "brain" of the engine. It controls many functions, including the fuel pump. A faulty PCM can send a constant signal to the pump. This is less likely but a possibility.
* Wiring Issue: A short circuit or damaged wiring in the circuit leading to the fuel pump can also cause it to run continuously. This might involve a frayed wire, a corroded connection, or a pinched wire.
* Fuel Pump Pressure Sensor: A malfunctioning pressure sensor might not correctly signal the PCM that there is enough fuel pressure, leading to the PCM keeping the pump running.
Troubleshooting Steps (in order of ease):
1. Check the Fuel Pump Relay: Locate the fuel pump relay (consult your owner's manual or a repair manual). You can often swap it with a similar relay (check the amperage rating) to see if that solves the problem. If swapping relays fixes it, replace the faulty relay.
2. Check the Inertia Switch (if applicable): Locate and reset the inertia switch.
3. Listen Carefully: Pay close attention to when the fuel pump is running. Does it run constantly even when the ignition is off? If it only runs *after* you turn the ignition on but keeps running, then the problem is likely the relay or wiring. If it's running constantly even when the car is off, it points more toward a wiring issue or a problem with the PCM.
4. Professional Help: If the problem persists after checking the relay and inertia switch, it's best to take your Riviera to a qualified mechanic. Diagnosing PCM problems or complex wiring issues requires specialized tools and expertise. A constantly running fuel pump can quickly drain your battery, and prolonged running can damage the pump itself.
Important Safety Note: Disconnecting the fuel pump directly can be dangerous due to the potential for fuel leaks and fire hazards. Always disconnect the power at the fuse or relay first before attempting any work directly on the fuel pump itself.
