under sec 20 sale of goods act:-
the property in the goods passes to the buyer when the contract is made, and it is immaterial whether the time of payment of the price or the time of delivery of the goods, or both, is postponed.
sec 33 :- putting the goods in the possession of the buyer or of any person authorised to hold them on his behalf is deemed to be delivery of goods.
it is immaterial that at the time of delivery whole or part amount is paid. so if you have delivered your car to the buyer then it is deemed to be delivered according to contract of sale, then you are not liable to renew insurance. you must file suit in civil court for recovery of sale amount and file a criminal case under sec 138 NI Act. once cheque is duly signed it is presumed that drawer of cheque is discharging his liability.