LAUNCH PAD V
User's Manual
87
inductance voltage of ignition coil maintains the conduction of
secondary circuit.
6) Contact point close the current fl ow into primary coil, the primary
coil oscillates due to the mutual inductance.
Primary ignition waveform
Section a shows the voltage oscillation on the primary circuit due to
the magnetic induction of spark in the duration;
Section b shows the damped oscillation generated by remaining
magnetic fi eld energy after the spark;
Section c shows the make contact magneting period of primary coil.
Seen from the waveform, the amplitudes of breaker contact closed
angle, break angle and breakdown voltage and spark voltage are very
clear, besides, the spark delay period and two oscillations can also
be tested. For the ignition system without faults, compared with the
whole cycle, the contact closed angle just 45%-50% (four-cylinder),
63%-70% (six-cylinder), or 64%-71% (eight-cyliner); the breakdown
voltage is over 15kv; the spark voltage is about 9kV, the spark period
is greater than 0.8ms. If these values or waveform are abnormal, it
means there is fault or the system needs to be adjusted.
7.4.2 Secondary-simultaneous ignition analysis
The following connection should be made before performing this
function:
1. Power the Scopebox on: Power is provided to the Scopebox in
either of the following ways:
• Power adapter: Insert one end of the power adapter into the
Power interface of the Scopebox, and the other end to the AC
outlet.
• Battery clamps cable: Plug one end of the power adapter into
the Power interface of the Scopebox, and then clamp the other
two terminals to the vehicle's battery (Red to +, and Black to -)
respectively.
2. Connect the B-shaped terminal of the data cable to the Scopebox
Data I/O port, and the other end to the Data I/O port of the
diagnostic tool.
3. Plug the BNC end of secondary ignition pickup into CH1/CH2/CH3/
CH4 channel of the Scopebox, and connect the high-voltage clip to
high-voltage line, and crocodile clips to ground.
High-voltage clips to
high-voltage line
Crocodile clips
to ground
BNC Connectors
to Channels
IA-2 below shows the valid and invalid ignition waveforms. Under
the working status of valid ignition, the breakdown voltage and spark
voltage are higher because the cylinder is fi lled with fresh combustible
mixture gas, which has a lower ionization level and vice versa.
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