MiDnIgHt RuMbLeR

I have a 1997 Dodge Work van with the 3.9 and 187,000 Km's on the dial. I just bought this truck 1 month ago and at the time did not notice or possibly did not care at the time about the engine knock.

The vehicle tends to crank over 4-6 times before she fires and when it does catch, I can hear this knocking sound coming from either the front of the engine or at the bottom and the sound does not go away. Sounds more in the front.

What might this issue be as I am new to the 3.9 and do not know a whole lot about the common problems with these engines.....