This has been spoken about a few time's. But there is a procedure for both types of LPG, to allow start up on LPG. Probably known by all LPG owners, but hey oh!
Mixer ring type:
1 - Switch the ignition on
2 - Rock the LPG switch over to the petrol position and then back to the LPG position. You should notice that the LPG Orange light is now on and not flashing
3 - Start the engine with your foot depressed on the throttle about 1/4 of the way to full throttle. It may take a few seconds for the engine to start as LPG has to be drawn into the engine.
Fuel Injected engines (post 2000) with sequential injected LPG:
Although the injected LPG system can be started on LPG, this should only be done if necessary - for example if your petrol pump is not working.
This can be done with this system by the following process.
1 - Switch the ignition on and press the LPG button to the petrol position.
2 - Disconnect and the re-connect the LPG switch.
3 - Holt the LPG button until the yellow LPG light comes on.
4 - Start the engine.