Here more info on your sensor, from the source:
Datasheet -- CSLA2CD
So just do the math. You might have to measure the actual values on your rig but lets assume for examples purposes that you have a 6 ohm injector, 2 volts hold voltage, 12 volts peak voltage:
You need a 2.5 volt rising signal and a 2.2 volt falling signal at the cpu to trigger on and off respectively (regardless of how the signal gets there, the input is a binary switch to the cpu). There is a 50k resistor in series with the pin.
sensitivity of sensor is 32.7 mV N* ± 3.0 @ 8 Vdc , 72 amps max (N=number of turns). Offset is vcc/2.
So all I can figure is that at 0 amps it reads 4 volts (8/2). and at 72 amps (one turn) it reads 8 volts. @32.7mv sensitivity that is 122 steps for half travel (hmm, sounds like an 8 bit conversion going on somewhere maybe).
Ok, so in this example for peak current we have 12 volts/6 ohms = 2 amps. So if we want maximum output signal we divide 72/2, and come up with 36, so 36 turns will have this sensor full on at peak. output should be about 12 volts, no extra amplification needed there it seems.
So how "on" is it at hold? Well 2v/6ohm=.333 amps. So the answer is "not very"
and now it has an offset.
This particular device, while handy for you, may not be an appropriate choice, if there are hall effect switches that won't require extra circuitry to undo the circuitry built into the device.
In order to keep this simple we need to locate one that can be on from, say, .2 amp on up, preferrably clamp on. That way anyone can use it instead of tapping injector wires.