gas conversion, wont run on petrol

[zacco]

Hi fellas, friends car, a make that wont be mentioned, 97 efi v6 ,runs on lpg but wont start or run on petrol . This looks like an aftermarket installation. Vehicle is mod plated and job seems to be tidy. Would anyone having any experience with these systems be able to point me in a logical direction for a fault finding exercise.
Disclaimer. I prefer diesels !
Cheers, zacco

[geeves]

If its been running dedicated gas then the first question has to be is there petrol to run on?

Did it use to run as dual fuel or has it never had petrol since the conversion?
If you take the fuel line off the injectors do you get petrol there?
My thoughts in no particular order
fuel pump
Ecu or conections
injectors (these can sieze if dry for too long)
timing (dedicated to lpg which would be more advanced than petrol)

[zacco]

Thanks geeves, found changeover relay circuitry was fried and immobiliser on key was cactus. Sorted