Cummins Diesel Forum banner

oil presure

5K views 22 replies 7 participants last post by  StealthDiesel 
#1 ·
I am sure this is a noob question, but none of my other diesels have done it and none of my co-workers seam to do it. When it is cool outside, truck starts just fine but as soon as I drive off it seems my oil presure is almost pegged, I normally let it warm a little befor I leave. The presure still does not come down untill it is almost compleatly up to temp. I try to baby it untill the presure comes down. Do I need to?
 
#3 ·
factory oil from dealership, it only pegs while driving untill it warms up than back to norm. This week is the first time my truck has seen below 10 and hopefully the last.
 
#4 ·
well, I guess i don't have a good explanation as to why it would be pegged so high. My only experiance is the gauge being at about 3/4 of the way up when it's cold and then settling back to just over half of its range (I think about 40psi). Maybe someone else will chime in here.
 
#5 ·
At what RPM does the gauge peg? And by peg, I assume you're saying it goes ALL the way to the right and could go no further, correct?

FWIW, I don't wind my engine out until it's up to operating temperature, keeping my oil pressure needle between the middle mark and the mark just to the right of it (high end of normal). I'm also running Rotella T6 5w40 synthetic.
 
#6 ·
with the 2003 and newer diesels, the oil pressure you see on your gauge is computed oil pressure, not your actual. Hook a manual gauge up to where your oil pressure sensor is and then you will have a much better idea.
 
#7 ·
Ummmm, no? Have any references to back that up? Any idea how the ECU would "compute" oil pressure without actually knowing what viscosity oil was being used?

It's true that the oil pressure gauge is CONTROLLED by the ECU, based on the reading it gets from the oil pressure sending unit, but it is not "computed" (aka "made up").
 
#10 ·
I am just going off of what my local cummins and dodge dealers informed me about 2003 and newer dodge cummins, 5.9 or 6.7
either way, it is not a bad idea to hook up a manual gauge and double check.
 
#13 ·
My understanding was that the 6.7L engines only had an oil pressure switch like the 5.9L trucks & that OBDII monitors wouldn't display oil pressure readings.


Yahooligan, does your Edge OBDII Insight give actual oil pressure readings?
 
#14 ·
It doesn't, but it doesn't show all the OBDII PIDs that are available, either. There are a number that are missing.

Also, there are a couple of P-codes for the oil pressure sensor that do apply to the 6.7, I don't know if these apply to the 5.9 or not:

P0521 Engine Oil Pressure Sensor/Switch Circuit Range/Performance
P0524 Engine Oil Pressure Too Low

I could see only P0524 if it were a simple on-off switch, but P0521 tells me it does more.

Those of you with a 5.9, does the gauge actually change with RPM or does it always stay steady?

It seems like an awful lot of work to make the oil pressure gauge on the 6.7 be fake but perform like a real gauge that does have different positions based on cold or hot oil temp as well as RPM. Sure would be simpler to just translate the sensor reading into a signal to be sent to the stepper motor in the gauge cluster like the ECU does for the other gauges.
 
#15 ·
If your Edge Insight doesn't show oil pressure, it is highly likely that the 6.7L does not have an actual oil pressure sensor.

The definitive proof for the 5.9L engines was the wiring diagram that showed that the oil pressure sensor was actually a switch.

As I mentioned for my 5.9L, I have an Autometer oil pressure gauge. It's tapped into one of the oil filter head ports.

The in dash gauge has a small range while the Autometer gauge shows full range.

For example, when my engine in cold my Autometer gauge shows 75PSI while the in dash gauge shows a little high.
When my engine is warmed up my Autometer gauge goes from 20PSI at hot idle to 70PSI at higher RPM. The factory oil pressure gauge barely moves.
 
#16 ·
If your Edge Insight doesn't show oil pressure, it is highly likely that the 6.7L does not have an actual oil pressure sensor.
The Insight is known to not show a number of PIDs that do exist, the lack of an oil pressure PID means nothing.

The definitive proof for the 5.9L engines was the wiring diagram that showed that the oil pressure sensor was actually a switch.

As I mentioned for my 5.9L, I have an Autometer oil pressure gauge. It's tapped into one of the oil filter head ports.

The in dash gauge has a small range while the Autometer gauge shows full range.

For example, when my engine in cold my Autometer gauge shows 75PSI while the in dash gauge shows a little high.
When my engine is warmed up my Autometer gauge goes from 20PSI at hot idle to 70PSI at higher RPM. The factory oil pressure gauge barely moves.
I'm not questioning the 5.9, I'm saying the 6.7 appears to be different. Couple that with the fact that you can easily find a replacement oil pressure switch for the 5.9 all the way up to 2006...but there's a mysterious lack of one for the 6.7.

All I'm asking is for someone with a 6.7 to tell me they have a mechanical gauge installed that doesn't match the dash gauge, then I'll shut up. :D Everything I can find, and everything stated here, relates to the 5.9 and yes, they use a switch.
 
#18 ·
No worries, still a good a discussion...

Good work finding that thread. The 6.7L aftermarket & in-dash oil pressure gauges shown in that thread behave identical to my 5.9L.
 
#19 ·
Don't be confused yahooligan....the engineers that followed the direction of their superiors are the ones I have a problem with....way to many guys have put real guages on their rigs and found the stock ones to be pretty much junk....6.7 or 5.9 no difference..sounds like some other posters got your interest up enough to dig deeper and prove my point
 
#20 ·
Ultimately that's always what I'm after, verifiable proof or references, though sometimes my instigation may not make it look that way. :D Everyone can afford to learn something new, nobody knows everything about everything.

In my field, "because I said so", "I've been doing it this way for years", etc doesn't qualify. :D So I'll keep looking until I find the truth or someone gets fired up enough to provide data to back up their claims. If all I get back are insult attempts then I think it's pretty clear what the other person is full of, and it's not knowledge! :thumbsup:

I'm hoping Edge will augment their EAS with an oil pressure sensor so I can get an accurate readout on the Insight. They say they'll be adding more accessories (sensors, etc) when they can.
 
#21 ·
By peged I meen maxed out by factory specs. You have low, then a hash mark, norm, a hash mark, then high/truely pegged. I am at the last hash mark if that makes any sence. The very end of the normal range, and it stays there above 1200rps and will not go down unless i idel or warm up to temp.

I will not pull out of my drivewayway untill im at, at least 50deg and I puut untill about 100deg.
 
#23 · (Edited)
Your original question kinda got lost in the technical discussion...Sorry about that...

Since the factory in dash oil pressure gauge is a fake, just ignore it unless it is reading zero.


Also, your signature says your truck is 07.5. So it must be a 6.7L but you might want to add that so it's totally clear.

Edit: Since your signature also mentions deletes & the 6 speed auto, it's actually totally clear! :)
 
#22 · (Edited)
There is a built in oil by-pass valve in the oil filter head on the 6.7 engines that is set to open at 80 psi. No matter what the oil pressure gauge reads when pegged the oil pressure never goes over 80psi.

With an Isspro oil pressure gauge, at idle & full warm up mine reads 25psi, at first start up in Winter at idle it reads 75-80psi.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top