On the 1997 2500 in sig. it has a knock when the motor is cold. and my MPG took a dive a little before this happened. has my timing sliped below stock or am i completly off?

 

no one?

also if you give it a little fuel to rase the RPM it goes away also

 

In some the posts I've read on lift pumps they can have a tendancy to "knock" or be noisy when on death row. Don't hold me to it but it's a thought.

If it does turn out to be the l/p JMHO but I'd rather change the fuel filter than have to change the l/p!

 

My first thought was the lift pump. I replaced mine at about 370k cuz it was ticking but saw no performance problems. I bought mine from a Case dealer, cost less than from Cummins but had to swap one of the fittings. If you do replace it don't forget the L-shaped hose (about $7 from the dealer) to the fuel heater. They come out as an assy anyway.