Don't think you can. I've got an e-gas system on a Range Rover I recently bought and there's no mention of it in the handbook that came with the car and holding the button in while cranking doesn't work either.
96 Saab 900XS, AEB Leo, sold
93 Range Rover 4.2LSE, Lovato LovEco, sold
97 Range Rover 4.0SE, multipoint, sold
98 Ex-Police Range Rover 4.0, AEB Leo, daily motor
96 Range Rover 4.6HSE Ascot, AEB Leo, my spare
It's been a while since I've tried so I just tested it on one of my own cars ... You switch the car to petrol (just red light on) turn the ignition off, press and hold the changeover button in and turn ignition on and crank , while cranking release button ..... That should work but be aware if its a cold motor you do run the risk of blowing injectors / ECU.
Andy
why is it you never see the headline PSYCHIC WINS LOTTERY !!!!!!!!
http://www.sstv.org.uk/autogas/index.html twitter ... @autogasandy .... With lots of conversion photos !! Facebook Andy Evans Autogas