I just purchased a 1998 with 12 valve. Driving home, if I idle too long oil pressuure drops to (0) momentarily then comes back to 40 psig. i checked oil and its only down, maybe a quart. Do i have sending unit, or oil pump issue here???

 

My bet is the oil pressure switch. They always start crapping out after100,000. And these engines wouldnt last 5 seconds with out oil pressure.Do it the rite way the first time and buy it from cummins, I think its close to 40 bucks. and its tricky to get to, so be patient

 

Check it with a mechanical pressure gauge to be sure but I would bet on the sender.
Does the OIL light come on when the pressure drops to "0 PSI”?

How do the rest of the gauges react at this time? I also have a wandering FUEL gauge occasionally.

Here is a link to my fix.

https://www.dieseltruckresource.com/...d.php?t=107789

Good Luck Jim

 

We replaced Sending unit and it seems to be okay.