On my way back from a roping, I come to a stop sign and, I will admit I never have looked at the oil pressure guage before, it dropped with the tach. Like I said I have never seen this before. It did this everytime I let the engine rpms down below 1800. I always saw it a little to the right of the 40 mark and last night it went to the left to the end of the black marks when I let off the throttle. This morning I never got the truck to 190* on the temp guage and it did not drop that far, but it would still drop a little. It is like it has something to do with engine temp. The hotter it is the farther it drops. The truck was running great last night, pulling the best I can remember, but this kind of conserns me. I looked at the dipstick this morning and it was full; the engine coolant beside the radiator on the other hand was full a few days ago and was below the first bump this morning.???

 

I have been told that the oil pressure gauge on our trucks are a "dummy" gauge. They do not accurately give you the oil pressure. They just read in a certain area on the gauge as long as the oil is pushing some minimum amount of pressure. Why I don't know. Seems silly to me. They should be in a gauge that is actually useful.

 

Texas CTD you are correct. The oil pressure gauges in our trucks are like stepper switchs; between x and y pressure indicate x, then between a and b indicate a. When I installed my oil bypass filter I was concerned about losing oil pressure so I installed a Autometer electric oil pressure gauge in a T beween the port on the standard Cummins oil filter adapter and the hose that goes to the bypass filter. I have found that between about 60 to 70 psi on Autometer gauge the instrument panel gauge indicated about 3/4 of the scale. Just below 60 psi on the Autometer gauge the instrument panel gauge indicates a tick above 40. I have not been lower than 40 psi on the Autometer gauge but the instrument panel gauge indicates 1/4 scale. Needless to say the instrument panel gauges are pretty inaccurate. Maybe DC should use a 3 color light system, green - good, yellow - fair, red - umm somethings wrong? With everything tied to the ECM we give up quite alot.

L8r,...........dogger

 

When fully warmed up, my engine is at 25psi at idle, sometimes a tick below that... When cruising at 65mph it is at 65psi.

 

I believe there is a new TSB that addresses this. I haven't been able to find much info on it yet. It is supposed to deal with oil pressure guage inaccuracy, white smoke on start-up and I think rough running on start up but am not 100% sure. I believe the TSB number is 18-041-05.

Like I said I haven't been able to find much info about this TSB but it is worth a shot. I would also put an oil pressure guage on to check the oil pressure to verify it is correct for your piece of mind.

 

I'll at least take it to the semi local Dodge house to get it checked. It maybe that I never payed attention to it, and it has done it all along.

 

Your oil pressure gauge is a complete farce.

Anything over 3PSI, and the ECM calculates what the oil pressure gauge should read by taking into account Engine RPM, and coolant temperature.

Your Cummins has tremendously higher oil pressure at all times than is what is indicated on your oil pressure gauge.

It is completely normal what your gauge is doing.

Once your engine reaches operating temperature, no matter what type of oil you are running, striaight 0w, or gear oil at 140w, your gauge will indicate the same oil pressure.

The TSB fix, is useless as well. Your oil pressure sensor is only a 3PSI Hobbs switch. On OR Off.

Merrick

 

So it will just go up and down depending on throttle and engine temp? Called the deal and they said it was normal. To think I am in the performance business and I have never paid attention to the oil pressure.

 

Yup.

Seems Cummins oil pressure is more reliable than DC's sender's...

The fix for 2nd gen trucks was a flash that did teh exact same thing, except there was a bug... If you stalled the truck, and left the key on, it would still indicate oil pressure. LOL

Merrick

 

6psig i believe is the switch setting, not 3psig...

 

It's not just the 5.9s in the dodge's that use an on/off switch for the oil pressure. I work for a large city and we have been using cummins engines in our backers and dumps for a number of years. A while ago I had a ISB 8.3 that was dying on the driver. I had to get it nice and hot (230) and just as I put it in gear the slight load would kill it. That's when I saw that the oil pressure gauge went from 43 PSI to 0 in a flash! (The trucks have a safety shut down in case of loss on oil pressure). After that we had a training class with a rep from cummins (better late then never!) and he told me that cummins got a big patch of bad pressure switches from there vendor. So someone said LET'E JUST USE A ON OFF SWITCH! He said that all the engines are shipped that way now and it's up to the body builder if they want to put a true pressure switch in. I just looked at him and shook my head.

Kenny K

 

So don't mind it unless is says 0(Uh ooo).

 

basically yes...