1. Low Fuel Level: The simplest reason is that you're simply running low on fuel. The fuel pump may not be able to draw fuel effectively when the tank is nearly empty.
2. Fuel Pump Relay: The fuel pump is controlled by a relay. A faulty relay can prevent the pump from receiving power. You can usually find the relay in the under-hood fuse box (often labeled). Try swapping it with a relay of the same amperage rating for another, non-critical circuit (like the horn, for example), to see if that fixes the problem. If the problem goes away, the relay is bad.
3. Fuel Pump Fuse: Check the fuse for the fuel pump in the fuse box. A blown fuse will also prevent power from reaching the pump. Replace it if it's blown. However, if it blows again immediately, there's a more serious short circuit somewhere in the system.
4. Inertia Switch: Some vehicles have an inertia switch (a safety device that cuts power to the fuel pump in a collision) often found under the dash or in the engine compartment. Check if this switch has tripped. There's usually a button you can press to reset it.
5. Crankshaft Position Sensor (CKP) or Cam Position Sensor (CMP): These sensors tell the PCM (Powertrain Control Module) the engine's rotational position. If they're malfunctioning, the PCM may not send power to the fuel pump.
6. Fuel Pump itself: The fuel pump itself could be failing. This is the most expensive option and usually requires dropping the fuel tank to access it. You'll likely need a mechanic for this one.
7. Wiring Issues: A broken wire, corroded connection, or poor grounding can interrupt the power supply to the fuel pump. This requires careful inspection of the wiring harness.
8. PCM (Powertrain Control Module): While less common, a faulty PCM can also prevent the fuel pump from functioning. This is usually diagnosed with a scan tool.
Troubleshooting Steps:
1. Check fuel level: The easiest and cheapest solution first!
2. Inspect fuses and relays: Use a multimeter to check for continuity (if you know how).
3. Locate and check the inertia switch: Reset it if necessary.
4. Listen for the fuel pump prime: When you turn the ignition key to the "on" position (but don't start the engine), you should hear the fuel pump briefly run for a few seconds. If you don't hear it, then the problem is likely before the pump.
5. Use a scan tool: A professional scan tool can help diagnose issues with the CKP, CMP, or PCM.
Important Note: Working with fuel systems can be dangerous due to the flammability of gasoline. If you're not comfortable working on your vehicle, or if you cannot pinpoint the issue, it's best to take your 2003 Ford Ranger to a qualified mechanic for diagnosis and repair. Don't try to guess and replace parts unnecessarily; this will just cost you more money.
