Fuel Injector Flyback

Fuel injectors are electro-mechanical devices, which use an electromotive force (EMF) to open the injector
and when it closes a reverse EMF is generated, this needs to be correctly handled by the VEMS electronics
or the voltage would burn out its delicate components. VEMS uses flyback diodes for this job, the type of
diode used depends on the Low or High Z configuration.

First we need to measure the resistance of an injector to find out what type we have, use your DVM to measure
the resistance across its two terminals.

The resistance of this particular injector is 12.8Ohm which means that this is a High Z (High Voltage) injector
Low Z injectors (low voltage) will read a much lower value between 2&5Ohm

Now we know our injector type we need to identify the correct flyback diode configuration to use. If you are
using multiple injectors on one channel or If you want to use PWM to drive the injectors the LowZ configuration
should be used.
For High Z injectors where PWM is not required, but this is not the recommended method, the High Z - High Voltage
configuration is used.

Low Z - Low Voltage

For Low Z Low Voltage installation the diode marked ES2J is used

And the orientation of the diodes on the board is as shown

High Z - High Voltage

For High Z High Voltage injectors the diode marked 332 6V8 is used

And the orientation of the diodes are shown here

Flyback lead

Finally we need to provide a path for the back EMF to go to, this is provided by a flying lead to pin 22 or 23 of
the EC36 connector. You will need to scrape the coating from the PCB track in the middle of the Flyback diodes and
solder a lead between the track and the pin on the EC36 connector: