I think he is asking about the pulse generators. On the '84 they are on the back of the engine. 85 and on they are under the timing belt covers. They are the two little black dudes next to the crank pully. You can test them by pulling the PG coupler. It is located under the left side cover. the one with the white/yellow wires are for cylinders 1&2 and the blue/white are for cylinders 3&4. The book says they should measure 1200 +/- 100 Ohms between the white-yellow or white-blue.