Here's how to test it:
1. Listen for the Pump:
* Key On, Engine Off (KOEO): Turn the ignition key to the "ON" position (don't start the engine). You should hear the fuel pump run for a few seconds. This is a prime test. If you don't hear anything, the pump might be faulty, the relay is bad, or there's a wiring problem.
2. Check the Fuel Pump Relay:
* Location: Find the fuel pump relay in your fuse box (usually under the hood, but check your owner's manual). The location and appearance vary slightly depending on the specific model of Dakota.
* Swap the Relay: Swap the fuel pump relay with a relay of the same amperage rating from a different circuit (one that isn't critical like a non-essential accessory). If the pump now runs with the swapped relay, the original relay is faulty. If not, the problem is elsewhere.
3. Check for Power at the Pump (Advanced):
* Safety First: Remember, you're dealing with fuel and electricity. Make absolutely sure the battery is disconnected.
* Access the Pump: Accessing the fuel pump usually requires dropping the fuel tank. This is a significant undertaking requiring special tools and knowledge. Consult a repair manual for your specific vehicle model.
* Wiring Diagram: Get a wiring diagram for your Dakota's fuel system. This will show you which wires go to the pump and what voltage they should have.
* Test with a Voltmeter: With the ignition key in the "ON" position, use a voltmeter to check for power at the pump's wiring connector. You should have battery voltage (around 12V) at the connector when the key is on. If you don't, the problem lies in the wiring or the relay.
4. Check Fuel Pressure (Advanced):
* Safety First: Again, disconnect the negative battery terminal.
* Fuel Pressure Gauge: You'll need a fuel pressure gauge designed for automotive applications. This gauge is connected to a test port usually located near the fuel rail (consult a repair manual for the exact location).
* Pressure Readings: With the engine running, the gauge will show the fuel pressure. The specified pressure will vary depending on your specific engine. Consult your owner's manual or a repair manual for the correct fuel pressure specification. Low pressure indicates a problem with the pump, filter, regulator, or a leak.
Important Considerations:
* Fuel Filter: A clogged fuel filter can prevent the pump from functioning correctly. It's a cheap and easy part to replace and should be checked first.
* Repair Manual: A repair manual specific to your 1990 Dodge Dakota is invaluable. It will have detailed information on fuel system components, locations, testing procedures, and specifications.
* Professional Help: If you're not comfortable working with fuel systems and electricity, it's best to take your Dakota to a qualified mechanic. Incorrectly handling fuel can lead to serious injury or fire.
By following these steps, you can systematically diagnose the problem with your fuel pump. Remember to prioritize safety and consult a repair manual for specific details relevant to your vehicle's model.
