EL 6 cyl Falcon wont start on petrol (starts on LPG and runs on petrol though)

[tandy ass]

Got a strange fault - Once a day I've been starting the car on petrol and driving it for a minute or so to keep the injectors alive, before switching across to LPG.

Over the past week its happened three times, the car has just been cranking without firing when on petrol. If you flick it to gas, it will start within about 5-6 seconds by the time the gas has made it into the motor from the mixer. If you flick it back to petrol it will run fine after its started.

Any ideas?

[Madhatr]

mine wouldnt start on petrol either, when the plugs and leads were replaced, problem went away.