I was reading the "Excel Preliminary Physics" book for NSW, Australia and it said that the flow of petrol through the hose actually creates a charge and since the nozzle is a conductor a charge is formed by the friction of the petrol and the nozzle. It also says that the hole is made so that when the nozzle goes in the car's body will make contact with the nozzle and earth the charge. It also said that if the contact with the car's body was made, a spark could be created that would ignite the petrol.
I was wondering that if you keep a hose with petrol on and ensure that the charge is not earthed, is it probable that you will create a spark and ignite the petrol or are the chances just too low and the conditions too specific?