My friendly Nissan parts guy photocopied some wiring diagrams for me
The engine has a camshaft position sensor which the ECM (ECCS Control Module)uses to work out when to fire the coil via a power transistor. The dizzy *only* routes the sparks to the plugs.
If one cylinder is firing then the dizzy is working, so your leads could be out of firing order. Try this:
The spark plugs are numbered 1-4 from the oil filler to the dizzy. The no 1 plug lead goes to the dizzy terminal facing the back of the engine bay adjacent to the oval connector. No 2 lead goes to the bottom of the dizzy, no 4 to the front, and no 3 to the top.
**Note this gives the correct firing order 1, 2, 4 then 3.**
If firing order okay, remove dizzy cap, inspect the 4 terminals inside for build up of white deposits, scrape off down to bare metal, check centre brush is spring loaded and free to move. Finally check rotor button (arm) clean it up too.
Also, some old dizzy caps can develop conductive hairline cracks/paths diverting the sparks away from the proper terminal and cause misfiring. You can only see the cracks inside the cap in bright sunlight. Then get a new cap. (I spent two weeks finding that out on my brother's car after replacing plug leads, points, condensor and rebuilding the carby!) LWC