Fuel injector signal

03-17-2013, 10:53 PM
A fuel injector (which is essentially an inductance), opens and sprays pressurized fuel into the engine when is activated by the PCM.
The circuit mentioned can be seen as a RL circuit.
Nevertheless, the signal or voltage in the fuel injector is not like seen in a RL circuit fed by a square power supply.

So here are my questions:
1) Of the two wires going to the injector one is held at steady 12 volts while the other lead is pulsed to ground by the ECM. The injector inductive kick reaches 55 up to 90 volts. Nevertheless, according to the Kirchhoff's Voltage Law, the total voltage around a closed loop must be zero. Does the injector driver hold the remaining 43-78 volts?
2) Is something wrong with the analysis of square wave applied to RL circuits seen in books? Why the signals are not similar as the expected? Where can I get a good analysis of a fuel injector electrical circuit?

Pleas somebody help me with this?!

Best regards!

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