Will crank sensor keep 350 from starting?

Yes, a faulty crankshaft position sensor can prevent a vehicle from starting. This sensor is crucial for the engine management system as it provides the engine control unit (ECU) with information about the position and rotational speed of the crankshaft. If the ECU doesn't receive this information, it may not send the necessary signals to the fuel injectors and ignition system, resulting in a no-start condition.