Yes there some really good stuff on that site how the zener set's the time it take's to close the injector.
This is done by using a zener diode across the PCM driver (transistor or MOSFET). See Figure 6.
As the magnetic field falls back into the injector winding the energy is allowed to loop through the circuit. This allows the current to diminish at a set rate. The lower the voltage is set by the zener diode, the more energy is allowed to loop through the circuit. If a diode were used rather than a zener diode, this would let the most energy allowed loop through the circuit.
A diode will allow the stored energy to loop until it reaches source voltage, in this case 12 volts. This would allow the injector the longest period of time to close. The higher the zener diode voltage, the shorter the period of time allowed for the injector to close. This is due to the energy looping through the circuit being cut off early by the voltage rating of the zener diode.
If a 65 volt zener diode is used, the energy that is looping through the circuit is stopped at 65 volts which is 53 volts sooner than a diode, that allows the energy to continue to loop through the circuit until it reaches 12 volts. So the energy from a higher rated zener diode will shut off the energy looping through the circuit sooner which allows a faster pintle closing rate. Likewise, the energy from a lower rated zener diode will allow the energy to loop longer which will cause a slower pintle closing rate. This rate is set by the zener diode voltage which is matched to the injector design.
The delay in closing voltage can be seen in Figure 2 Part H on page 27. Once the Pintle starts to fall through the magnetic