My car can not start on petrol but start on cng with autometic mode

[pwuser171786618248]

when i start it only on petrol it can not be start what the reason my cmg is end and how to start my car?

[Xulfiqar]

Are you capable of testing fuel, spark and compression yourself?

[Moderator]

car make & model.
usually mechanical fuel pumps fail in cng vehicle after prolonged idling at constant pressure. When needed these pumps fail to produce enough pressure to fuel the carb for immediate start up. idling engine switch over to petrol can take place. but dead dry fuel pot in carb may not load enough fuel from weak mechanical pumps.