I don't know what it is about my wife and my truck, but she drove it to Tucson from Las Vegas, and today she called me to tell me the oil pressure gauge is reading very low. (Last year the Crank Position Sensor died when she drove it there) She checked the oil level, and it's near the top line, well above the 'safe' line. She also mentioned the oil still looks quite fresh, but it should, since I changed the oil a couple days before she left. I've searched the forum, and can't find any threads indicating a REAL oil pressure problem, but the SENSOR seems to fail sometimes.
My question, now that I finally get to the point, is: Is there ANY history of oil pressure problems with the Cummins? I really don't want to ride 800 miles to change a sensor out, but I also don't want to find out the hard way that the oil pressure REALLY IS low. The truck has only 152,000 miles on it, so I can't believe it's worn so badly it needs a new pump or complete rebuild.

TIA
Jim

 

It needs to be checked. Check for a Cummins or Freightliner shop in the area...unless there's a DTR member in Tucson to personally check it out.

The Oil Pressure Sensor is just to the rear of the ECM, about middle of the driver's side of the motor.

 

Mine broke 50,000Kms ago it stays on the high mark all the time even with key on engine off. the ecm guesses as to where the oil pressure actually is, it is NOT an accurate gauge, if your worried have someone test the actual pressure with a mechanical gauge. or stick another sensor in it to see if it changes, be fore warned the sensor aint cheap, IIRC it was 80$-150$ at a local cummins and dealership. even the aftermarket one were not cheap.

 

The 99 will have a real oil pressure sensor. Sometime in 01/02 they went to a pressure switch.

 

97 was the last year of real pressure readings. Everything newer went to the instrument cluster "buffering" the reading to what the driver "should" expect to see!

 

So, all gauge readings (engine temp, voltage and oil pressure) after 97 are not accurate? Can you explain in a bit more detail what instrument cluster buffering does?

Thanks.

 

Talked with the wife again today. She confirms oil level is right at the 'full' line, when parked on a level surface. She also started it and drove while talking to me. The pressure gauge reads around two-thirds of max at idle (cold), and drops off when she brings up the rpm. It picks back up once she lets it return to idle. Sounds to me like the sensor (or something in the signal train between it and the gauge) has become vibration sensitive. I've never seen a motor that had an actual pressure drop when engine rpm was increased, and I've worn out my fair share of engines. I'll get out there in the next couple weeks and check the pressure with a mechanical gauge, and see what's really going on.

 

The instrument cluster only buffers the oil pressure. Basically due to an excessive amount of customer complaints about what the oild pressure "should" be, and what the guage reads, and also because of what a lot of customers described as "excessive" fluctuation.

From what you described, I'd bet on the sender!. But.....I have seen more than one engine ( especially on Dodge and Jeep!) that had the paint flake off of the inside of the pan and clog the oil pickup screen. Slow the RPM down, or shut the engine off, and the pressure would return due to the lack of high flowing oil. Never have seen it on a Cummins, but there is always that chance. Save some cash and just have her find any kind of a reputable shop and have them do an oil pressure test on the truck with a manual guage. Simply take the plug out of the oil filter housing ( right on top of where the filter screws on ) and screw in a guage. Have them document actual guage readings at numerous RPM's and temperatures, and go from there. Shouldn't charge more than 25 - 50 bucks. Heck.....price a sender replacement.....maybe just have her get it done and see if it changes? You'd have more piece of mind ( I know I would!) with your wife driving such a distance.

 

Grider Pirate,
The Oil pressure sensor is a part that commonly fails on the older ISB series of engines. It is a simple change, only about 5 minutes.
Takes a long arm and a 32mm deep well socket.

When the part fails it usually reads zero pressure and throws a code immediately.

I would definitely have someone manually check the pressure as listed above.

 

Yep, probably a sensor. I had the exact same issue w/my gasser. Much easier to replace on the ctd.

 

Yup! Sensor.
Talked to my wife again last night. As it usually turns out between us, most of my anxiety was caused by mis-communication. She didn't say the needle deflects to the right, she didn't say it goes way up. What she said was it goes "all the way to pointing at the oil can symbol". It's pegging, not dropping off. I really hate talking to my wife about stuff like this, in the end it always ends up pissing me off.