320i W/N Start
Check the fuel pump relay on the fusebox. It is the black plastic relay between the two mounting nuts for the air cleaner. This relay energizes the fuel pumps when it receives pulse signals from the distributor. The purpose of this relay is to cut off the fuel pressure in a major collision in which the engine stops. When the engine stops, the pulses from the distributor stop and the fuel pumps are both de-energized. The relay is by-passed when the key is in the START position.
This relay can be somewhat pricey, so do some troubleshooting before you buy a new relay. Here's how: Remove the relay and you will notice it has four prongs; three larger ones and one smaller one. Install a jumper wire between the two middle prongs which are perpendicular to one another. This would be the large prong toward the front of the car and the large prong closest to the engine. Turn the ignition on and the fuel pump will come as well. If the pump comes on, go ahead and start the engine. If it runs, the relay is defective and needs to be replaced. You can drive the car with the jumper wire in place of the relay, but if you're involved in a collision and a fuel line is ruptured, the fuel pumps could keep pumping fuel to a potential fire. That's a bad thing.
Last edited by galaxyflier; 04-19-2010 at 12:25 PM.