* Faulty Fuel Pump Relay or Circuit: Even with a new pump, a bad relay (the electrical switch that activates the pump) or a problem in the wiring leading to the pump can cause intermittent operation. The relay is a cheap and easy part to replace or test.
* Low Fuel Pressure Regulator: This regulates the pressure of fuel going to the engine. A faulty regulator could intermittently restrict fuel flow.
* Clogged Fuel Filter: A partially clogged fuel filter can restrict fuel flow enough to cause starting problems, especially when the engine demands more fuel under load.
* Fuel Pump Wiring Harness: Check the wiring harness for damage, corrosion, or loose connections between the fuel pump and the relay or engine control module (ECM).
* Intermittent Crank Sensor or Cam Sensor: These sensors tell the engine's computer when to inject fuel. A faulty sensor might cause an intermittent lack of fuel injection.
* Faulty ECM (Engine Control Module): While less likely, a malfunctioning ECM could send incorrect signals to the fuel pump or other systems, resulting in intermittent operation. This is usually a more expensive repair.
* Improper Installation of the New Fuel Pump: It's possible the new fuel pump wasn't installed correctly, leading to poor contact or other problems.
What to do:
1. Check the fuel filter: This is the easiest and cheapest thing to check first. A clogged filter is a common cause of intermittent fuel delivery.
2. Test the fuel pump relay: This is also relatively simple. You may need to consult your vehicle's repair manual or online resources to find its location and test it.
3. Check the fuel pressure: A fuel pressure gauge connected to the fuel rail can measure fuel pressure. Low or fluctuating pressure indicates a problem with fuel delivery.
4. Inspect the fuel pump wiring: Look for any signs of damage, corrosion, or loose connections.
If you're not comfortable performing these checks yourself, take the vehicle to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately. Simply saying "the fuel pump was replaced" doesn't solve the underlying issue. The mechanic needs to investigate the *why* the car is still having fuel delivery problems.
