BMW E90 3-Series Fuel Pump Testing for 325i, 325Xi, 330i, 330xi, 328i, 335i

Introduction

This tutorial will guide you through testing the fuel pump in your BMW E90 3-Series models (325i, 325Xi, 330i, 330xi, 328i, 335i). A faulty fuel pump can lead to poor engine performance and starting issues. By following these steps, you can determine if your fuel pump is functioning properly, ensuring your vehicle runs smoothly.

Step 1: Gather Necessary Tools and Parts

Before starting the testing process, gather the following tools and parts:

• Tools:

  • Phillips screwdriver
  • Flathead screwdriver
  • 10mm socket
  • Digital Volt Ohm Meter (DVOM)
  • Test light

• Parts (if replacement is needed):

  • Fuel pump
  • Fuel pump sealing O-ring

Make sure you have an assistant to help with the testing process.

Step 2: Access the Fuel Pump Electrical Connector

1. Remove the Rear Seat Cushion:

   • Locate and lift the rear seat cushion to access the fuel pump electrical connector beneath.

2. Locate the Access Panel:

   • Find the access panel that covers the fuel pump terminals.

3. Remove the Access Panel:

   • Use a screwdriver to remove any screws securing the access panel and take it off carefully.

Step 3: Test the Fuel Pump Voltage

1. Connect the DVOM:

   • Set your DVOM to measure DC voltage.
   • Connect the DVOM probes to the fuel pump terminals according to the wiring diagram.

2. Activate the Fuel Pump Control Module:

   • You can activate the module by using a BMW scan tool or by attempting to start the vehicle. This will send control voltage to the pump.

3. Read the Voltage:

   • Observe the voltage reading on the DVOM. You should see approximately 10 volts, which indicates the module is functioning correctly.

4. Assess the Pump Functionality:

   • If the correct voltage is present but the pump does not activate, it is likely that the fuel pump is faulty.

Step 4: Conduct Fuel Pressure and Volume Testing

1. Remove the Engine Cover:

   • Take off the engine cover over the fuel injectors to access the fuel rail.

2. Connect a Fuel Pressure Gauge:

   • Connect a fuel pressure gauge to the fuel rail following the manufacturer's instructions.

3. Measure Fuel Pressure:

   • Have your assistant press the Start/Stop button while you observe the pressure reading on the gauge. Make sure it meets the specifications for your vehicle’s model.

4. Check Fuel Volume:

   • If fuel pressure is adequate, you can also assess fuel volume by disconnecting the fuel line and measuring the amount of fuel pumped over a set period.

Step 5: Clear Fault Codes

After completing the testing and any necessary repairs, it’s essential to clear any fault codes. Use a BMW scan tool to ensure that all systems are functioning correctly.

Conclusion

By following these steps, you can effectively test the fuel pump in your BMW E90 3-Series. If you discover that the fuel pump is faulty, consider replacing it to restore your vehicle's performance. Always ensure to check and clear fault codes after completing your repairs. For more detailed guides on maintenance and repairs, visit the Pelican Parts Technical Article Directory.