* Faulty Fuel Pump Relay: The relay controls the power to the fuel pump. A failing relay might provide intermittent power, causing the engine to die. This is a cheap and easy part to replace.
* Bad Fuel Pump Wiring: A short circuit or corroded connection in the wiring harness leading to the fuel pump could interrupt power. Inspect the wiring for damage, especially near the tank.
* Fuel Filter (Clogged or Restricted): Even with a new pump, a clogged fuel filter can restrict fuel flow enough to cause stalling. This is a relatively inexpensive part to replace.
* Crankshaft Position Sensor (CKP Sensor): This sensor tells the engine's computer the position of the crankshaft. A faulty CKP sensor can prevent the engine from starting or cause it to stall.
* Cam Position Sensor (CMP Sensor): Similar to the CKP sensor, a bad CMP sensor can lead to starting and stalling issues.
* Ignition System Issues: A failing ignition coil, ignition module, or distributor (if equipped) can cause the engine to cut out unexpectedly.
* Fuel Pressure Regulator: This component regulates fuel pressure in the system. A faulty regulator could allow too much or too little pressure, causing problems.
* Mass Airflow Sensor (MAF Sensor): While less likely to cause a sudden stall, a faulty MAF sensor can provide incorrect air/fuel mixture information to the engine computer, potentially leading to stalling.
Troubleshooting Steps:
1. Check the Fuel Pressure: This is crucial. A mechanic should test the fuel pressure at the fuel rail to confirm the new pump is actually delivering sufficient pressure. Low pressure even with a new pump points to a problem elsewhere (filter, regulator, etc.).
2. Inspect Wiring: Carefully examine all wiring related to the fuel pump, including the relay. Look for corrosion, breaks, or chafing.
3. Check the Fuel Filter: Replace it even if it looks okay. It's a cheap preventative measure.
4. Have the CKP and CMP Sensors Checked: These sensors are common culprits for intermittent starting and stalling problems.
5. Test the Fuel Pump Relay: A simple swap with another relay (if possible) can quickly determine if the relay is the problem.
It's essential to have a mechanic diagnose the issue properly. Simply replacing parts without diagnosing will be expensive and may not fix the problem. The fuel pressure test is especially important in this situation.
