Try this excerpt from other author. I replaced the sensors (crankshaft & camshaft) but still won't start and I found out that the engine wiring harness from the Engine Control Module (DME) to the engine control module relay box was charred.
1998 BMW 323i won't start
A customer brought her BMW 323i to our shop with a complaint that it will not start. She says that she went inside the store and when she got back in the car, the car it would not start. We use the new "Modis" scan tool from Snap-on and there are no codes stored in the memory. I believe that it could be either crank or cam position sensor. Would I be on the right track? I used the live monitoring on the scan tool, and checked the engine speed while cranking and the value of "zero" did not change which is what leads me to believe that it could be a sensor.
Has your shop checked for fuel and spark? If no fuel, then check the fuel pump relay, pump fuse, then the camshaft position sensor. If no ignition is present, check the crankshaft position sensor. A faulty crankshaft position sensor will cause the engine not to get fuel or ignition. Has it rained in that area by any chance? If so, check the DME for flooding as well.
No rain this time of the year. We did check for spark by spraying carburetor cleaner through the airflow sensor. No nothing. Where are the sensors located? Is there an electrical diagnosis that I can do to verify the non-operation. Do you know the ohms reading and continuity?
I am not able to give you values on the ohms reading at this time. The crankshaft position sensor is located at the front of the block, right above the crank pulley. The camshaft sensor, on the other hand, is located under the intake manifold.