Settled: Your Oil Pressure Gauge is Fake

[Matt400]

Where can I hook up an aftermarket mechanical or electrical oil pressure gauge to get real readings

On top of the oil filter housing.

I prefer mechanical

IMO electrical is better, less chance for a leak and if you use a quality gauge & sender it will be accurate.

 

[RMachida]

Ok, guys. Let's take this to the next step for us newbies. Where can I hook up an aftermarket mechanical or electrical oil pressure gauge to get real readings off the Cummins? I prefer mechanical but the location to place the tube or sensor should be the same so where do you guys recommend???? I want to know what that baby is really doing!

For example, unless I am confused, the "pressure switch" is mounted to the side of the block near the ECM. What would be the disadvantage of installing a "T" fitting there? There has been a lot of discussion of uusing a fitting on top of the oil filter housing. Is there a reason why one would be preferred over another?

 

[nickleinonen]

For example, unless I am confused, the "pressure switch" is mounted to the side of the block near the ECM. What would be the disadvantage of installing a "T" fitting there? There has been a lot of discussion of uusing a fitting on top of the oil filter housing. Is there a reason why one would be preferred over another?

no disadvantage using a tee fitting where the factory "sending" unit is. hard part though, try finding a metric M14x1. 5 ORB tee fitting... much easier to use one of the other 3 ports on the main gallery. there are 4 total, one in use and one blocked. 2 are M10x1. 0 ORB fitting, 2 are M14x1. 5. one is blocked by a steel bracket, and the other is in use by the factory switch. the small ones are both accessable from above the engine. one is right below the cp3, one is right above the ecm. i wanted to use the port below the cp3, but the hose i used touched the cp3 pump, so i have mine coming off the one above the ecm...



actually for me, i prefer measuring the pressure off the main gallery... and it leaves the port on top of the filter pad open for a lube oil temprature gauge...

 

[RMachida]

Thanks for the info. You answered my next question as well, the thread sizes.

 

[67guzzler]

Jay, I didn't think you were contradicting Ryan. But, never the less the oil pressure gauge is pretty lame for a $40,000+ vehicle!

Cools. No worries. I just wanted Ryan to know that too.

 

[KevinWatts]

... ... I bet the reading when warmed up is probably close to actual if measured with a mechanical gauge. My '05 gauge mimics my '96 gauge pretty close under similar conditions.

Sometimes... I put a mech oil press gauge on and sometimes it matches right up and sometimes it's off by 40psi. The factory gauge seems to hover around the center of the readings more than the mech. On morning warmup, even in summer the factory gauge starts centering out quicker than the mech. I'll be pushing a solid 80psi and the factory gauge will say 50ish. One thing that is of some importance is initial cold startup. The factory gauge goes up quickly, while the mech gauge takes a little time. I always wait until the mech gauge is up to pressure before driving off, and that is usually at least 10-15 seconds longer than the factory gauge says its ready.



... And sometimes when the engine is all warmed up and I'm just cruising down the road the gauges will match perfectly.



Kevin

 

[rbattelle]

the small ones are both accessable from above the engine. one is right below the cp3, one is right above the ecm.

You can also get to it through the wheel well if you remove the wheel well liner (I have to do it this way... I have some things in the way in my engine compartment that preclude getting to the port from above). Good luck if you accidentally drop your fitting down in between the ECM and the engine block... I speak from experience.



Anyway, I think the code required to make the needle dance in a way that's consistent with "customer expectations" is probably not very many lines. If I were doing it, I'd probably take an engine in the lab with real sensors on it and collect oil pressure, water temperature, RPM, and maybe ambient temperature data. Then run a linear regression analysis on all those variables. That would give one simple equation that relates all 3 (or 4) parameters. A couple lines of code (assuming the ECM software is written in C or something similar), then, allows the ECM to compute oil pressure with very little overhead.



My experience with my aftermarket gauge is very much like Kevin's - after warmup at highway speeds the factory gauge and the aftermarket gauge read pretty close to the same. This would be consistent with a regression-type analysis, which would have a best match around the middle of the operating envelope.



I'm sure there are other ways of programming it. It sure does it's job very well, as JGann points out.



-Ryan

 

[Allnew2Me]

It isn't just the new trucks, my 2001. 5 is the same way. I have the factory manual and it says the very same thing regarding the gauge reading what the computer tells it to according to "customer expectations".

 

[Kirwin]

Factory vs aftermarket oil pressure gage

I have a Cyberdyne digital oil pressure gauge teed into the oil rail on the side of the engine on my 03. I realize this is not the correct way, but I used a 1/8" brass nipple and some pipe dope and carefully threaded the fitting into the block just tight enough to prevent leakage. After I installed the gauge, I was concerned as oil pressure at idle, hot, after a hard pull on the interstate sometimes falls below 6 psi for about 30 seconds and them slowly climbs back to around 15 psi as coolant temperature falls as the engine idles. I routinely see this when pulling my travel trailer in hot ambient temperatures. I'm not saying that oil pressure is really that low as I'm not sure how accurate the gauge is at such low pressures. I know that my 97 with the same Cyberdyne model gauge has never fallen below 17 psi at idle hot and normally reads right at 20 psi at idle. At highway speed they both read between 55 and 60 psi depending on coolant and to some degree ambient temperature. All of these pressures are hot temperatures. I agree with Ryan that the factory gauge does not always correspond to actual oil pressure (no matter how good the computer program they wrote to simulate it) and I'm convinced he is correct with his testing. Now the real question, WHY did they put an IDIOT LIGHT with numbers on it in the dash. Another thing Cummins own publications specify a minimum oil pressure of 10 psi at idle. SO who picked the 6 psi set point of the in dash IDIOT LIGHT? IMHO Ken Irwin

 

[TSpecht]

Here's a thought. For better protection/early warning, what would happen if one were to substitute perhaps a 10 or 15psi switch in place of the stock 6 PSI switch? I suppose we'll never find a way to program it so we could use an actual transmitter, but maybe a switch which closes at higher pressure might be a little better? Just wondering if anybody has pondered such a thing.

 

[sag2]

I can't help myself anymore reading this thread so here goes (again)

When was the last time anyone on this board had an oil pressure related failure on the engine?

If I recall, it is slim to none, and slim just left!

I think it's great that you guys care enough about your truck to want to know what the pressure is, but the bottom line is, more than 6 psi is enough PERIOD.

You can make yourself crazy watching a real gauge, so unless you hear Cummins is having oil pressure problems, why are you so concerned?



And a class action suit? How were you harmed?



Most on this site love their trucks, and just performing regular maintenance will keep them running happily for many years to come. I think that is more important to the longevity of your engine than an idiot light that looks like a gauge.



OK, I'm done

 

[rbattelle]

When was the last time anyone on this board had an oil pressure related failure on the engine?

If I recall, it is slim to none, and slim just left!

I think it's great that you guys care enough about your truck to want to know what the pressure is, but the bottom line is, more than 6 psi is enough PERIOD.

Generally speaking, I agree, Sag. I don't have an aftermarket gauge because I fear an oil system failure, I have an aftermarket gauge because I like knowing my oil pressure. That's my personal expectation.



Ken brings up an outstanding point, however, that the specification in the service manual is 10 psi minimum at idle. The dummy should at least be set to 10 psi rather than 6.



I hate slow-reacting factory oil pressure gauges, and I hate fake ones even more. BTW, as far as I know Ford's been using fake oil pressure gauges for some time; it's not just a Dodge thing. My ranger factory gauge needle pointed to exactly the same spot no matter what the ambient or engine conditions were. They might as well have just painted the needle on it.



-Ryan

 

[Matt400]

When was the last time anyone on this board had an oil pressure related failure on the engine?

It has happened. A fella posted an incident where an oil filter was left loose at an oil change and it wiped out his engine before he could catch that the gauge dropped to 0. My sons 03 will idle at 50+ psi where the OEM gauge will show the same even if it only had 6 lbs.



If you developed a leak in a turbocharger line you might see an unusual pressure drop and check things out, the OEM gauge won't let you know of any pressure drop till 5. 9 psi when it drops from (consumer preferred) normal to Zero.

the bottom line is, more than 6 psi is enough PERIOD.

Are you sure about that? I wouldn't want to be running down the road with 7 or for that matter 37 psi when idle produces a higher pressure, something would be wrong IMO.

You can make yourself crazy watching a real gauge,

I don't think anybody wants to watch it, just doing a visual once per day a real gauge has the ability to show warning signs.



I do see your point though, it can be overkill like putting a temp gauge on a differential... oops, did I say that? I will probably get thumped on that one!

 

[Matt400]

They might as well have just painted the needle on it.

:-laf :-laf I shouldn't laugh at that cuz its probably next.

 

[cyborg]

I I think that is more important to the longevity of your engine than an idiot light that looks like a gauge.



OK, I'm done

And we finally found it. The "appearance above performance" customer.



"We don't care whether it works as long as it looks like it does. "



I watch (glance) at my instruments when driving. As every professional driver does. Do you think hotrodders started installing pyrometers? NOT! Truckers have used them for years. Oil pressure gauges have saved more than one motor.



But more to the point is that a few people have had oil system failures go undetected resulting in fried motors, directly attributed to the "pretend gauges".



There are more people unaware of this little fraud than know about it. They actually think it's measuring pressure!!! That is a far cry from showing zero every six minutes.



Sorry, I don't mean to be harsh, it's just wrong on several "motorhead" levels.

 

[67guzzler]

I agree. I remember reading on this board something to the effect that a person who was entering the interstate and he reported a loud noise and then afterwards the oil pressure gauge went down to 0. By then he'd shut down but he had no prior warning. I hope I have the facts straight but he was clearly someone who could have benefitted from a good oil pressure gauge. I think doing something "wrong" is worse than not doing it at all. Just put a dummy light up there like my Ford Escort. That would be better.

 

[sag2]

Actually I heard that the gauge for 06 was going to be changed to not move like the earlier models did. It was going to go to a pre determined point and stay there. No more moving around based on engine speed and temp. And actually, the factory gauge/light does give an audible warning if the switch grounds from lack of pressure. The only thing I don't like is the delay from the time it grounds to the time the cluster lowers the needle and turns on the chimes. But then even if I was running a manual gauge, I would have to be looking at it at the time of failure. So I guess the best idea is to have both anyway. But for me the factory gauge (uh light) and chime is enough.

And don't laugh, they probably will just paint the needle on if they can save some money!

 

[Diesel Nut]

Well if I run 60 psi at freeway speeds with a trailer and the switch is set for 6 lbs, I would think damage has been done when that sucker hits 0. Also, lets factor in how long it takes you, the driver, to realize you are at 0 and pull over ang shut down. Ptretty expensive motor. One more exaomle of how our lives are run by those who are to stupid to know the differnence. If you freak out beacuse you roil pressure gauge moves a little it time for you to sign up fo an AUTO SHOP class took in high shool. Don't insult the aware because there are ignnorat suckers out there . . . .

 

[cyborg]

It's not that you are consciously looking at it. The minds eye monitors it. Your mind will catch a major fluctuation and say "HEY DUMMY, Thats not right!!".

I know that I consciously check my instruments at start up and shut down. A habit from filling out daily check sheets on trucks for thirty years.



I paid extra to have the ability to monitor the condition of the various systems. If it is not what they sold me, it's fraud. Prima Facia.

I paid for more, they gave me less.



There should be an advisory

: This instrument is decorative only, reminiscent of a bygone era, do not rely on it's findings. ,

kind of like an H2.

 

[nickleinonen]

and a true oil pressure gauge can help you catch a fuel diluted oil situation [somewhat of a scare on these engines]. once you get a custom to knowing what the pressures should be at any given temprature, you will notice something is out if you are above or below those numbers. an excessively low pressure idling hot [say 6. 5psi] could be fuel dilution, or a failed oil pressure regulator spring [hey, it could happen] or something more serious. but according to the factory gauge, you wouldn't know anything.



i have caught fuel dilution at work by oil pressures before we got the latest samples back from our oil lab [located onsite, but only operates m-f 0800-1600]. something looks a little odd, and it gives you some warning to take a closer look at things. .