I have a no start issue?

Hi I'm busy with a 2004 e46 320d, the previous guys changed the motor and now it does not start. I have run an ISS scan and the crank sensor was faulty. Replace the sensor and cleared out the fault code successfully. But after cranking the motor the sensor fault returns on my diagnostic meter. I have checked for fuses relays broken wires ect. As soon as i spray quickstart in the air intake then it wants to fire up but still fails to start. The starter motor also sounds a bit slow. Should I just try and tow the car till it starts or is there something I'm over looking?