It's 50-50 you can hardly tell only by the timing factor. However, from my experience I noticed that when someone checks instantly on some of the streets (flop, turn or river) out of the position, this is often a sign of weakness and he is ready to give up the hand on almost any bet. This is true especially when playing online small buyin-tournaments (up to 10-15$). And my logic behind this is the following:
if the next card or cards that pop up (flop, turn or river) improve your opponent hand in same way, it's normal for him to slow down and take some time before making his decision- whether to bet for value, semi-bluff or check to trap, check for pot control etc. An instant check in most cases means that he is rather weak and this card is insignificant to him. So, a bet here will win the pot more often than not.