diesels and oil pressure

rickjf wrote:
Hi all,
having an oil pressure problem and I know there are many knowledgeable folks here. First, the basics.
its a 2012 gmc duramax with about 57,000 miles. We're full timing
so a lot of miles are towing a trailer. oil is not leaking, it is
not low. had oil changed 2000 miles ago.
pressure will be fine, and then, slowing for traffic, a stop sign or
light etc, the gauge will momentarily to 0, a chime goes off, and then it goes back up. I went to a dealer in Oregon a few weeks back,
and they said it was the sending unit, and we replaced it. Well, it happened again yesterday so its not fixed.
any ideas?

Sounds like a weak oil pump to me. Secondly there are two sensors it is possible that they replaced the Oil Level sensor not the Oil Pressure sensor.

Check that first. If it was me I'd replace that oil pump if there was any chance it could be worn or bad. Have them clean it out first and give it a test drive.

This happened to me too. Climbing a grade and then left off the throttle, Normal pressure is 23 and alarm goes at 9. I brought it to a dealer and no issue. I found hundreds of people online with the same issue. I don't think you have a problem, GM just has the alarm and operating pressure too close together and a momentary dip below 9 psi set it off.

Here is a post from the Diesel Place.
"I am guessing the oil level sensor is where to start as the zero pressure reading may be programmed in by GM to motivate you to add oil when it is low. Stupid logic but the gauge is numb from 9 PSI to ~30 PSI in the same spot so...

You would get a DIC of "low oil pressure stop engine" at 9 PSI or lower. As you don't have this message I bet it is low oil level sensor or related wires."
Hope this helps.
Dave

As a follow-on to the above comment - check and make sure the dealer installed the correct filter.

On edit. In fact, I think I would change out the filter and add a qt of oil and see if that cures the problem.

You had no problems until the last oil change. In a situation like this, I always look back at the last change that could have caused the problem. In this case I wonder if they installed the wrong filter or if maybe the check valve in the filter is somehow malfunctioning and periodically stopping the flow of oil out of the filter. I know this isn't supposed to happen but . . . . . . .

I used to have a Duramax and remember how high the oil pressure ran. If it's not the oil pressure switch, then it seems like something is drastically affecting the flow of oil. In my opinion, the first item on the list would be the oil filter, especially since you recently had it changed.

I would think even the wrong wt oil would not cause a problem like you are experiencing.

darsben wrote:
WATCH THIS VIDEO

Yes this may be a gasser, but if you are using a cheap filter it is a possibility.
In my Cummins i run Factory Fleetguard filters, yep about $12, but they are the one designed for the engine. I buy mine at Cummins NW.

this did not happen before the last oil change, nor
about 1500 miles after. the oild is topped up properly.
oil change was at a gmc dealer, so "assume" they put proper
spec oil in.

darsben wrote:
WATCH THIS VIDEO

Gas engine, not a diesel.

copy and paste
https://www.youtube.com/watch?v=n7Q6QrT9nFE

Go to www.dieselplace.com
It is a GM Duramax and Allison forum, similar to this one, that specializes in issues with GM diesels and transmissions.

My first question: Did it do this prior to the oil change?? If it didn't, did they put in the correct amount of Oil, the correct weight, and the proper spec Oil??
If it was doing this before, forget everything I said.