LAUNCH
X431 PAD Scopebox User’s Manual
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of engine mechanical parts, fuel system components, and ignition system
components. Different parts of the waveform can specify that some
components and systems on the specific cylinder have faults. Refer to the
instructions for various parts of waveform for the related component working
status of specific waveform section.
Test methods and conditions:
Start the engine or drive the vehicle accroding to the driving performance fault
or poor ignition, etc. Confirm the consistence of judgement standard (the
amplitude, frequency, shape and pulse width, etc., for each cylinder), check
the fault of the waveform for corresponding components.
Waveform results: observe the ignition coil at the beginning of charging, the
relative consistent falling edge represents the dwell angle and ignition timing of
each cylinder are precise.
Ignition line:
Observe the height consistence of flashover voltage. Too high flashover
voltage (even out of the oscilloscope screen) represents a high resistance
existed in the ignition secondary circuit (for example, open circuit, or damaged
spark plug or high voltage line, or too large time gap on spark plug), while the
too short sparking voltage represents the resistance of ignition secondary
circuit is lower than normal value (due to pollutant and broken spark plug or the
high voltage line of spark plug has electrical leakage, etc.).
Spark or combustion voltage:
Observe the consistence of spark or combustion voltage, as it represents the
consistence of spark plug and the air-fuel ratio of each cylinder. In case that
the mixing ratio is too lean, the combustion voltage will be lower than normal
value.
Combustion line:
Observe the spark or the combustion line which shall be clean with few clutter,
as lots of clutter indicates the cylinder has poor ignition due to ignite too early,
damaged nozzle, pollutant spark plug, or other reasons. The duration of
combustion line indicates the mixing ratio of the cylinder is abnormal lean or
