[Richard]

The troubleshooting journey is narrowed down to one of two root causes. The first is that the sensor is not putting out a reliable signal. Turning it with a drill will answer that question. The second is that the drive tang is not turning the sensor. That could be caused by one of two things. The first being the tang is not properly seated in the sensor. The nut that mounts the sensor to the engine is actually a turnbuckle style affair. The problem with tightening it down is that the engagement of the tang in the sensor slot is blind. The second cause could be the tang engagement with the engine is stripped. Any further investigation requires the sensor to be removed and Clarke is suffering from THE crud. Unfortunately I think I gave it to him.