NIPPONDENSO Electronic Ignition System: Operation

1979 Toyota Pickup SR5SECTION Operation

As the timing rotor turns with the distributor shaft, its teeth (one for each engine cylinder) pass the pick-up coil assembly. See Fig 1. As the air gap changes with the passing of the teeth, the magnetic field varies creating a signal in the pick-up coil assembly.

The ignitor senses this signal and turns the ignition coil primary circuit on and off. This causes voltage to build and collapse, resulting in a voltage surge in the ignition coil secondary circuit that fires the spark plugs.

Fig 1: Toyota Transistorized Ignition Circuit Schematic
G09351010Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.