I was driving today and my check guages bell went off. I looked down and I had no oil pressure. I stopped and checked my oil. It was full. I waited for about 30 minutes and started it back up and the warning was still on. I put it in gear and all of the sudden I had oil pressure. On the way home the guage was fluctuating up and down and I lost pressure again as I pulled into the driveway. Is the oil pump going out?? Is it an expensive repair (1999 2500 cummins)?--rbond

 

Start by checking the wire from the gage to the sending unit. Make sure it doesn't have any loose connections or possibly rubbed the insulation off somewhere and is grounding out. After that I'd check the sending unit.

 

There is a very high probability that the sending unit is bad. This was a very common problem with the trucks around these years. I think Dodge even had a TSB on doing a reflash to make the gauge read around 40psi all the time if I remember right. Most folks say the oil pumps in these engines are pretty bullet-proof. If I recall,,,, the sending unit is right pricey also.

On Edit: After doing some checking. Click here for the TSB However, this TSB doesn't cover the 99 but I would still check the pressure with a mechanical gauge and also the wiring as Totallyrad stated above.
You can also use the Search function with the keyword "oil, pressure, sending, unit " and that should give some other threads to read.

 

I got mine flashed and all it does is make the guage a dummy guage. It sits up at 40 psi at all times. Before the guage would show a realistic change in pressure after the RPMs started to build. Now it just stays at forty until I shut her down. I am told that all you need to do is get the Cummins sending unit. Check some of the earlier posts by using the search. Also check my earlier threads on that same issue at https://www.dieseltruckresource.com/...ight=srtdiesel
Hope this helps your issue.

 

You need a sending unit.... I replaced mine around 75K and have lost count of how many I've done at work.

 

I'd just get a quality aftermarket oil pressure gauge and be done with the factory idiot gauge.

 

the cummins oil pumps are a gerotor style. very durable, and very little to go wrong. the usually only fail if they ingest a large amount of metal debris, in which case, you would be hearing that.