headgasket went on my 1998 Marea 1.8 16v,done the gasket,changed cam belt etc,after sitting during the rebuild the car battery went flat,put new battery in it,car did start and then would n't.No Spark but getting fuel,have both keys red and blue and the yellow code light goes out while spinning the engine.Mechanic reckons either Cam Sensor or Crank Sensor to be reason for no spark-Would this be correct?Which one of these supplies the spark.Thanks.Mark