This guide explains how to use the independent 2-channel ground method provided by the VMI3 to simultaneously measure 4 injector waveforms using only 2 physical channels, and how to compare and analyse the injection time and voltage status of each cylinder.
Guide Video (English)
Step 1: Connecting Probes for Simultaneous 4-Channel Measurement
The VMI3 allows the (+) and (-) terminals of a single channel to be used as independent measurement sources. Using this, connect all four injector control lines.
- Test Vehicle: Seltos (SP2) G2.0 MPI
- Injector Control Line Connections:
- CH.A (+) Probe: Connect to No.1 injector control line (A1 waveform on screen)
- CH.A (-) Probe: Connect to No.3 injector control line (A2 waveform on screen)
- CH.B (+) Probe: Connect to No.4 injector control line (B1 waveform on screen)
- CH.B (-) Probe: Connect to No.2 injector control line (B2 waveform on screen)
- Common Ground: Connect the black common ground clip of the oscilloscope to the battery (-) terminal.
Step 2: Oscilloscope Screen and Trigger Settings
- Measurement Range: Voltage 80V / Time 1.0 ms (to observe injector operating voltage and injection time)
- Peak Mode: To avoid missing high surge voltages that momentarily spike when injector operation is cut, turn on
[Peak Mode]. - Keep the engine at idle.
Step 3: Injection Time and Voltage Analysis
Intuitively compare the characteristics of the four injector waveforms aligned on the screen.
- Injection Time: Compare the length of the section where the waveform drops and stays near 0V to check whether the amount of fuel injected into each cylinder is consistent.
- Counter Electromotive Force (CEMF) Surge: Check whether the peak voltage (e.g. around 50~60V) generated when the coil magnetic field collapses is evenly produced in all injectors. If the peak voltage is too low, internal coil damage in the injector may be suspected.
Comments
0 comments
Article is closed for comments.