I've read the posts about oil sending units, but mine isn't going to 0 and maximum. It just fluctuates all over. Sitting at a steady idle, guage will suddenly go up to about 80 then back down to 40 or so. It always, so far, comes up when I speed up engine. Could this also be a sending unit. If it were the oil pump itself, I don't think my pressure would suddenly come up when idling. Any thoughts?

Thanks,
Steve

 

The gauge in the instrument cluster is not real!

You'll need a DRB Scan Tool to determine the actual oil pressure. 5.9ISB's should be governed at 65psi on the high side and you should see no lower than 25psi at idle.

 

Chances are your sender is goin' goofy. Not a big deal, easy to replace. Go to Cummins and get the sender. "The part number is 4088390NX
It costs around $70.00 and no reflash involved. This was for a 1999. Not sure if all the 24 valves use the same sender." I copied and pasted this from another thread. It makes it easier when you have the part number.
Tom