Symptom: a Shanghai Volkswagen Santana CNG rental car can not start.
    Troubleshooting: the first preliminary inspection of the car, start the engine running, but the car without any signs of the car, and then unplug the central cylinder line to flash test, the result is no high pressure fire, which determines the car can not start Ignition system has some trouble.
    Then the car's ignition system for further inspection, unplug the three-wire plug on the plug, plug in a new distributor, turn on the ignition switch, turn the distributor, you can see there is no high pressure fire, but you can hear the fuel The fuel flow from the work of the electric petrol pump in the pipeline, thus determining that the distributor in the ignition system has transmitted the signal to the engine control unit, instructing the pump to operate, indicating that the signal line of the Hall sensor to the engine control unit in the distributor , The fault should be in the engine control unit to the ignition coil line.
    Then use a multimeter to check the primary and secondary coil resistance of the ignition coil, the primary coil resistance is about 0.6Ω; the secondary coil resistance is about 5kΩ, indicating that the ignition coil is normal. In order to further verify the inspection results, in turn bring the new ignition coil plug, launch the vehicle, still no high pressure fire, thus determining the fault range in the engine control unit control ignition coil control line.
    Santana CNG car ignition system and ordinary Santana ignition system and fuel injection system has a greater difference in the Santana CNG sedan, the engine control unit to control the ignition coil drive voltage is not directly to control the ignition coil, but the ignition The signal is passed to the ignition time regulator. When the engine is switched to the gas state, the CNG control unit controls the ignition timing adjuster to make the necessary adjustments based on the ignition timing provided by the engine control unit, and ultimately the ignition timing adjusts the ignition coil to complete the flashover operation.
    According to the circuit diagram to check the ignition time regulator power supply and ground voltage between the normal; check CNG control unit to the ignition time regulator signal line connection is normal, thus to determine the ignition time regulator damage. With the accessory, the ignition input of the ignition timing regulator and the output pin are shorted directly, the engine is operated to the fuel state and the engine is started, and the ignition is normal. This verifies the failure judgment result of the ignition regulator.
    Replace the new pieces, smooth troubleshooting.