Signal Waveform

The three waveforms below are taken from injectors No. 1 and No. 4. The upper waveform is from the high-pressure (supply) side of injectors No. 1 and No. 4, the middle signal is from the low-pressure (ground) side of injector No. 1, and the lower waveform is from the low side of injector No. 4. The middle waveform is the same as the upper one because there is no ground for the circuit. When no current flows in the circuit, injector No. 1 is not energized and fuel does not flow. The lower waveform shows that ground is supplied and there is a voltage drop across injector No. 4. When current flows in the circuit, injector No. 4 is energized and fuel flows.