MPI – Troubleshooting
13-29
<Explanation of waveform>
The injector power supply voltage waveform shows a voltage drop caused by resistance of the resistor.
As the amount of current increases, voltage gradually decreases and a spike occurs at the plunger fully
opened position due to counter emf.
<Waveform observation points>
Point A: Voltage drop during fuel injection time (Refer to abnormal waveform example 1.)
Difference from standard waveform Possible cause
Voltage drop during fuel injection time is small (there
should normally be a voltage drop of about 10 V).
Resistance of resistor is too small. Resistance of injector
is too large.
Point B: Spike when plunger is fully open (Refer to abnormal waveform example 2.)
Difference from standard waveform Possible cause
No spike when plunger is fully open Plunger inoperative
<Abnormal waveform examples>
D Example 1
[Cause of problem]
Resistance of the resistor is too small.
[Waveform characteristics]
Small voltage drop
D Example 2
[Cause of problem]
Plunger is inoperative.
[Waveform characteristics]
No spike when plunger is fully open.
7-4 IGNITION COIL
Perform the same steps as with the conventional 4G9 engine
for the inspection.
Abnormal waveform
Normal waveform
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