* Crash safety: The pump shuts off to prevent fuel leakage in a collision.
* Overheating protection: The pump might have a thermal switch that cuts power if it gets too hot.
* Low fuel pressure: A sensor might detect dangerously low fuel pressure and shut down the pump.
If your fuel pump is *not* working, the problem likely isn't a tripped "shutoff" but a malfunction somewhere in the system. Possible causes include:
* Fuel pump relay: This relay switches the power to the fuel pump. A bad relay is a common and relatively inexpensive fix. You can test the relay by swapping it with a known good one (from a similar circuit in the car, if possible).
* Fuel pump fuse: Check the fuse designated for the fuel pump in your fuse box (consult your owner's manual).
* Fuel pump itself: The pump could be worn out or faulty. This is often the most expensive repair and may require professional help for installation.
* Inertia switch: Some cars have an inertia switch (often located under the dash or in the engine compartment) that cuts power to the fuel pump in a collision. Check if this switch has tripped. It usually has a button that you can reset by pushing it.
* Wiring issues: Look for broken, corroded, or loose wiring in the circuit running to the fuel pump.
* Fuel pump pressure regulator: A faulty regulator might be causing low fuel pressure, leading to the pump shutting down (though this is less common as a primary cause of the pump ceasing to function).
* Computer/ECU issues: In less common scenarios, a problem with the car's computer could be interfering with the pump's operation.
Before attempting any repairs: Disconnect the negative terminal of your car battery to prevent electrical shocks.
To troubleshoot: You'll need a multimeter to test the relay, fuse, and wiring. You might also need a fuel pressure gauge to check fuel pressure, although this is generally more involved. It's recommended to consult a repair manual specific to your 1990 Plymouth Sundance for detailed diagrams and testing procedures. If you're not comfortable working with automotive electrical systems, take your car to a qualified mechanic.
