Air Flow Meter – Hot Wire

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Reference waveform

Figure 6.5.4

Example Waveform

Figure 6.5.5

Notes:

When the positive fired plug kV's are recorded on distributor Ignition Systems (DIS), the voltage should be

as shown and not inverted, as this would suggest that the wrong lead has been chosen.

While the engine is running, the plug voltage continuously fluctuates and the display moves up and down.

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Follow these steps:

1. Click “Vehicle->Diagnosis”, as illustrated in Figure 6.5.2

2. Click “Ignition->Secondary-> Secondary DIS(Positive-fired)”,click “OK” , as illustrated in Figure 6.5.3.

Figure 6.5.2

Figure 6.5.3

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Warning: When attaching or removing secondary ignition pickups from damaged HT25 leads there is

a risk of electric shock. To eliminate this danger, attach and remove the secondary ignition pickup with

the ignition turned off.

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Connect the oscilloscope

1. Plug an auto-ignition probe (HT25) into channel 1 on the DSO3064(A).

2. Clip the lead's crocodile clip on suitable earth.

3. Fit the HT clip on one of the engine's positively-fired plug leads.

If the live waveform is missing or upside-down, you have selected a negatively fired plug. Either choose a

different plug lead or load the secondary negative waveform from the drop-down menu.

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The modern engine with Distributorless Ignition System (DIS) has all the advantages of a constant energy

electronic ignition system, but with the added bonus of the distributor cap, king lead and rotor arm being

removed from the system. Reliability problems from dampness and tracking are now almost eliminated.

DIS has its own drawbacks by having half of the plugs firing with an acceptable negative voltage, while the

other half are fired by the less acceptable positive polarity. This has the effect of increased plug wear on the

positive fired plugs.

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The voltage measured at the spark plug is the voltage required to jump the plug gap in varying conditions.

This voltage is determined by the spark plug gap, rotor air gap, etc.

The plug kilovolt (kV) requirement of older engines tends to be lower than that of the modern engine, as the

later designs run higher compression ratios, leaner air/fuel ratios, and larger spark plug gaps.

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Secondary-Distributorless (Positive Fired)

Technical information

Ignition coil is also referred to as a spark coil and used to transform lower voltages of power to the higher

voltages of power required to fire a system's spark plugs. It is similar to an electric transformer, consists of

primary and secondary winding circuits. Inside the coil's primary winding is the secondary winding. This is

coiled around a multi-laminated iron core and has approximately 20,000 to 30,000 turns. One end is connected

to the primary terminal and the other to the coil tower.

The ignition probe(HT25) voltage is produced by mutual induction between the primary winding and the secondary

winding, with the central soft iron core intensifying the magnetic field between them.

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Example Waveform

Figure 6.4.5

Notes:

Neither wire of the injector should be connected to the negative (ground) input of the oscilloscope as this could

cause a short circuit.

The 20:1 Attenuator is used to monitor the induced voltage that is created when the earth path to the injector is

removed. This voltage will be in the region of 60 to 80 volts.

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Reference Waveform

Figure 6.4.4

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Operation Steps:

1. Open the software, select “Vehicle->Diagnosis->Setup”, as illustrated in Figure 6.1.2.

2. Click “Sensors->Injector Diagnonis -> Single-point Injector(Voltage)”, and click “OK”, as illustrated in Figure 6.1.3.

Figure 6.4.2

Figure 6.4.3