Check the inline-pump that is located under the car. These tend to malfunction, but the engine will still run if the tank is not near empty. With the additional thickness of biodiesel, the fuelsystem needs the extra effort provided by the inline-pump to provide enough fuel at the correct pressure to the high-pressure pump.

You can try a metal rod against the side of the inline-pump and your forehead to listen if the pump is working or not. It should start to build up pressure for a couple of seconds when the key is turned to II. Have a friend turning the key without starting the engine.