Franklin said
“I have no doubts that I shall enjoy as much of both as is proper for me. That Being who gave me Existence, and thro` almost threescore Years has been continually showering his Favours upon me, whose very Chastisements have been Blessings to me, can I doubt that he loves? And if he loves me, can I doubt that he will go on to take care of me not only here but hereafter?” This to some may seem presumption ; to me it appears the best grounded hope ; hope of the future built on experience of the past.
George Whitefield: The Life and Times of the Great Evangelist of the Eighteenth-Century Revival, Vol.2 by Arnold Dallimore, page 449
In other words, he mistook general providential care for being in a state of grace. He failed to realise that God causes His sun to rise on the evil and sends rain on the unjust (Matt. 5:45).
Franklin doubted the deity of Christ (though Jesus made it clear that failure to recognise who Jesus was would lead to eternal death – John 8:24) and the Bible as the Word of God.
He remained in unbelief
After Whitefield ’s death
“Mr Whitefield used to pray for my conversion, but never had the satisfaction of believing that his prayers were heard.”
Ibid 453