I have a 1991 190E 2.6 with 214,000. Whenever I start is up in the morning, it taps for a few seconds until the oil pressure goes from 0 to the top peg. (about 3 seconds) . This is a new occurrence lately. The oil filter has been changed along with the oil (Castrol 20 w 50). Is this the oil pump, lifters or timing chain? Any insight would be greatly appreciated.