Hello.
Not sure if you familiar how cars work,but voltage rise when you start the car. For example with engine off your voltage will be 12-12.5V , with engine ruining 13-14.5V .You can set FMB ignition source as POWER Voltage and adjust at what Voltage you wan to see Ignition ON. As a default it set to 13.2V ,alternately you can take multimeter to measure your OBD output beetween PIN16 (+) and PIN4(-) with engine switched ON and OFF and determine voltage jumps .
Regards
Teltonika support