Fuel Pump Related:
* Weak Fuel Pump: The pump might be failing. Even if you hear it running, it may not be generating sufficient pressure to deliver fuel effectively to the engine. This is common as fuel pumps wear out.
* Clogged Fuel Filter: A clogged fuel filter restricts fuel flow, starving the engine. This is a relatively inexpensive and easy fix.
* Fuel Pump Relay: The relay might be failing to properly supply power to the fuel pump, even if you hear a whirring sound. A weak relay can sometimes give intermittent operation, making diagnosis tricky.
* Fuel Pump Wiring: There could be a break or short in the wiring leading to the pump. Check the wires for damage, especially near the tank where they are subject to movement and abrasion.
* Low Fuel Level: While seemingly obvious, ensure the tank isn't near empty. Some fuel pumps require a certain minimum fuel level to operate effectively.
Other Potential Causes (Even if the pump is activating):
* Crankshaft Position Sensor (CKP): This sensor tells the computer the engine's rotational position. A faulty CKP can prevent fuel injection, even if the fuel pump is working.
* Cam Position Sensor (CMP): Similar to the CKP sensor, but this sensor monitors the camshaft. A faulty CMP can lead to similar problems.
* Mass Airflow Sensor (MAF): A faulty MAF sensor provides incorrect air/fuel mixture data to the computer, leading to poor or no fuel delivery.
* Fuel Injectors: The injectors might be clogged or failing, preventing fuel from being sprayed into the cylinders. A fuel pressure test will help determine this.
* Computer/PCM Issues: A problem with the Powertrain Control Module (PCM) can prevent it from signaling the fuel pump or fuel injectors to operate correctly. This is less likely but possible.
Troubleshooting Steps:
1. Check the Fuel Filter: This is the easiest and cheapest thing to check first. Replace it if it's dirty or clogged.
2. Check Fuel Pressure: Use a fuel pressure gauge to measure the pressure at the fuel rail. This will tell you if the pump is delivering adequate pressure. This is crucial for determining if the pump is the actual culprit.
3. Inspect Fuel Pump Wiring: Look for any signs of damage or corrosion.
4. Check Fuel Pump Relay: Swap the fuel pump relay with a known good relay from another circuit (if you have one, use the owners manual). If the problem goes away, replace the relay.
5. Have a Mechanic Check Sensors: If fuel pressure is good and the pump/wiring/relay are okay, it's time to look at the engine sensors (CKP, CMP, MAF). A mechanic with a scanner can read codes for sensor failures.
6. Consider the PCM: This is usually the last resort, as it is expensive to replace.
Important Note: Before working on the fuel system, always disconnect the negative battery terminal to prevent accidental sparks. Fuel is highly flammable. If you're not comfortable working on your vehicle's fuel system yourself, it's best to take it to a qualified mechanic.
