Using Oscilloscopes on Vehicles

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(2) If the secondary waveform breakdown voltage is too high, and there is no good discharge process,
the spark of the relatively steep stage, as shown in Figure 3, indicating that the secondary circuit
resistance is too large, may be secondary circuit open circuit, poor contact or spark plug gap, sub-fire
head and distributor gap is too large and other causes. This failure may occur in every cylinder waveform,
may also appear in a cylinder waveform.







Figure 3 secondary line resistance is too large

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3 secondary ignition fault waveform analysis

It should be noted that a lot of fault performance in the waveform of each cylinder, but also some fault performance
in a single cylinder waveform.
Here are some typical fault waveforms.


(1) If the secondary waveform is inverted (the waveform of each cylinder is the same), as shown in Figure 2, the ignition
primary line is reversed.









Figure 2 a line reverse

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(1) Spark time is less than 0. 8m s reasons:

a. High voltage line resistance is too large;

b. Spark plug gap is too large;

c. Sub-disc and sub-fire head gap is too large;

d. Mixed gas too thin;

e. Spark plug temperature is too cold;

f.  Ignition timing is too slow;

g. Cylinder pressure is too high;

h. Valve spring is too weak.

(2) Sparking time is higher than 2. 4m s reasons:

a. High voltage line resistance is too small;

b. Mixing ratio too thick;

c. Spark plug gap is too small;

d. Cylinder pressure is too low;

e. Spark plug temperature is too hot;

f. Engine oil consumption;

g. Ignition timing too early;

h. The valve clearance is too small.

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2.3 Combustion line analysis


Observing sparks or burning line should be very clean, no excessive clutter on the combustion line, excessive clutter indicates poor cylinder ignition,
The reasons: premature ignition, injector damage, spark plug dirty or other reasons.


2. 3. 1 Burning time test conditions

(1) The engine running up to normal operating temperature;
(2) Adjust the engine speed to 2000r / m in.


Normal standard spark time 1. 5 ~ 2. 4ms (distributor system ), in the absence of distributor ignition system, the standard spark time must be 8 ~ 1. 8m s or more.

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(2) If the individual cylinder ignition voltage is too high, it may be the end of the cylinder pressure line is not inserted in the end,
the distributor cover dirty dirty or distributor cap jack electrode and sub-fire is not the same heart, The high-pressure cylinder
jack electrode gap is too large or the cylinder spark plug gap is too large, spark plug damage caused by other reasons.


(3) If the ignition voltage of each cylinder is too low, lower than the lower limit, it may be spark plug gap of each cylinder is too
small, the spark plug electrode oil, ignition coil performance is poor, the battery voltage is insufficient or the capacitor capacity
and other causes.


(4) If the individual cylinder ignition pressure is too low, it may be the cylinder spark plug clearance is too small, spark plug
electrode oil or spark plug insulation properties caused by poor and other reasons.

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2.2 secondary ignition voltage analysis

Check whether the breakdown voltage changes to meet the needs of the engine operating conditions change;
Check the breakdown voltage in the cylinder can be consistent between the various; through the breakdown
voltage level to determine the ignition system fault.
Breakdown voltage level with the cylinder pressure, the concentration and pressure of the mixture, the ignition
system secondary circuit resistance. The following is divided into four cases for failure analysis and judgment:


(1) If the ignition voltage of each cylinder are too high, exceeding the upper limit of the specified value, it may
be too mixed or too thick mixture, distributor central high-voltage line end is not inserted in the end or distributor
cover dirty, Distributor cap socket electrode gap is too large or each cylinder spark plug gap is too large and
other reasons.

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2 Secondary ignition waveform fault point analysis

The measured engine ignition waveform display, the first should be with the standard wave

Shape control. If the measured ignition waveform exactly the same as the standard waveform, said

Ming fire system technical condition is good; if the measured waveform is abnormal, that

Ignition system or other system fault, should be different according to the ignition waveform

Failure to reflect the area, diagnosed the cause of the malfunction.

2. 1 Ignition coil charging part

Observe that the ignition coil remains relatively constant at the beginning of charging

The falling edge of the waveform indicates the consistent closing angle and ignition of each cylinder

When accurate, if not coincidental, ultra-poor too much to prove that the super-poor cylinder ignition line

Circle controller bad ground or performance degradation. If the falling edge is a slope,

Then the controller power tube performance degradation or poor grounding; view

Whether the closed angle of each cylinder can be consistent; check the closing angle of the large

Small whether the engine operating conditions the size of the correct adjustment.

WisdomAugust

2 secondary ignition waveform fault point analysis

The measured engine ignition waveform display, the first should be with the standard wave

Shape control. If the measured ignition waveform exactly the same as the standard waveform, said

Ming fire system technical condition is good; if the measured waveform is abnormal, that

Ignition system or other system fault, should be different according to the ignition waveform

Failure to reflect the area, diagnosed the cause of the malfunction.

2. 1 ignition coil charging part

Observe that the ignition coil remains relatively constant at the beginning of charging

The falling edge of the waveform indicates the consistent closing angle and ignition of each cylinder

When accurate, if not coincidental, ultra-poor too much to prove that the super-poor cylinder ignition line

Circle controller bad ground or performance degradation. If the falling edge is a slope,

Then the controller power tube performance degradation or poor grounding; view

Whether the closed angle of each cylinder can be consistent; check the closing angle of the large

Small whether the engine operating conditions the size of the correct adjustment.

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Secondary coil waveform analysis principle: When the ignition, the secondary coil produces a high voltage,
when the voltage gradually increases to a certain value, the spark plug spark (test spark energy performance
for the blue-white flame, and can continue 1. 5 ~ 2.4 ms (distributor system), in the absence of distributor
ignition system, the standard spark time must be 0. 8 ~ 1. 8ms or more.


This flame in the cylinder of high energy, fast propagation, the rapid combustion of the cylinder full, explosive
pressure, the engine power output high), this voltage is the ignition voltage. Then the voltage drops rapidly to
another voltage value and maintain a period of time, the voltage is the combustion voltage, the combustion
time is the voltage is maintained at the combustion voltage value of the time. At the end of the burning time,
the energy in the ignition coil is basically exhausted, and the residual energy forms damped oscillation on the
coil. The number of oscillation waves is required to be more than 3 (standard 5 to 6).

Ideally, the secondary waveform is very stable, indicating that the voltage at each ignition firing is the same.
The graphics of each cylinder should be roughly the same. However, the actual situation is not ideal, the graphics
will always have larger or smaller jitter, such as ignition or breakdown voltage fluctuated, burning time may vary,
these do not necessarily indicate that the engine is faulty. This third Gao Lu and: secondary ignition waveform in
the application of fault diagnosis 7 will require our accumulated experience, combined with other test data
comprehensive analysis.

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Secondary coil waveform analysis principle: When igniting, the secondary coil generates a high voltage,

when the voltage gradually up to a certain value, the spark plug spark (In the test, the spark energy show

a blue-white flame, and last 1. 5 ~ 2. 4 ms (distributor system). In the non-distributor ignition system,

the standard spark time must be above 0. 8 ~ 1. 8ms. Such a flame in the cylinder owns high energy,

fast propagation, the rapid combustion within the cylinder Full, explosive pressure, engine power output

high), this voltage is the ignition voltage. Then the voltage drops rapidly to another voltage value and

maintain a period of time, the voltage is the combustion voltage, the combustion time is the voltage is

maintained at the combustion voltage value of the time. At the end of the burning time, the energy in the

ignition coil is basically exhausted, and the residual energy forms damped oscillation on the coil.

The number of oscillation waves is required to be more than 3 (standard 5 to 6).