Engine oil pressure

[jimm1009]

A while back I picked up my truck and the oil pressure was pegged out to the max side.
When you turn power on the gauge is at Zero. When the engine is started, it eventually goes to about 60 psi or so and the pegs out.
In my trouble shooting, I pulled the instrument panel down to check the wiring for looseness and correct installation. I cleaned and checked the ground. I checked the connection at the sending unit. No obvious problems were found.
I installed a temporary power wire from the transmitter unit to the gauge. No changes there so I installed a temporary ground wire next and still no changes. Well, most of the time when this happens in a system with and electric transmitter, the transmitter is then considered to be bad or inaccurate so I ordered a new one from one of our dealers / members.
I ordered and received what the parts manuals stated that I needed.
I installed the new transmitter and the problem still exists...nothing changed.
I have a question about my new unit. It is not marked with any numbers as is the old unit. Further more, it is slightly different from the old one that is marked with the MS part number. the connection on the new one is on center with the threads which is on center with the body of the unit. The old unit has the connection off center with the threads and the center of the body. I know that this is not of real concern due to the fact that this unit is new and it could be a design change or simply an upgrade or a different manufacturer.
Attached is a PDF picture of the unit. The one on the left is the old, original unit as delivered by Uncle Sam and the one on the right is not the new one but is exactly the same size and appearance but a 60 psi unit for an M38 jeep. I used it for the comparision picture due to the actual new unit being installed in the engine.
The engine oil pressure still pegs out to the max side. I have not checked the system with a mechanical pressure gauge because it is hard to find one for 120 psi in the generic automotive parts houses. I will do that next but in the mean time, help.. I've fallen and I can't get up! Is there any possibility that this is the wrong new unit since there are not markings or labels installed on it? I have to ask since it is a small possibility.
Jim

 

[CCATLETT1984]

I bet you have a bad gauge, but I wouldn't be running that truck until you got a real gauge on it. If a oil passage is blocked you could be building that much pressure.

 

[319]

You should be able to rent an engine oil pressure test gauge from a good auto parts store. KD Tools #3343 goes up to 300 psi.

 

[Boatcarpenter]

You can tee in a mechanical op gauge to use as a benchmark while you check out senders and gauges etc. Here is a pic of mine which is now about a 2 year "temporary" installation. It's about a $5 domestic water system gauge from the plumbing section at my local hardware store. Works great until I get a 120 sender and gauge installed.
BC

 

[m16ty]

You may have a 60psi sending unit witch can peg out a 120psi gauge. I've never seen a sending unit that didn't have the psi (60 or 120) on it (that's not to say there aren't some). With a 60psi sender and a 120psi gauge if your oil pressure is 60 the gauge will show 120.

 

[jimm1009]

Well about a week & a half ago I posted the problem that I was having.
I finally got around to having weather that I could work in and no longer having to pick up limbs from the last Hurricane here in Loose-my-banana.
I purchased a 200 psi water well gauge for a very temporary test on my engine.
I hooked up a barbed fitting to the oil pressure port along with some engine oil hose and a 200 psi water well gauge and bled the air. I got about 85 psi pressure while cold but only ran the engine for about 45 to 60 seconds. It seems that I would have about 65 psi at idle and cold (about 850 rpms).
I now know that I have a problem that is most likely the electric gauge since I have installed a new pressure sending unit. I did question the sending unit that I recently received due to the similar appearance to the 60 psi unit. See pics of new and old above.
Guess I will be purchasing a new gauge and going from there.
I'll post again when I receive and install my new gauge and get the system back to the way Uncle Sam intended it to be.
My only question now is that would you other owners out there simply give up on the electric oil pressure indicating system and go to a mechanical gauge?
If so, what gauge would you use that would look similar and have illumination too?
As always, any recommendations would be greatly appreciated.
Jim
jimm1009@yahoo.com

 

[jimm1009]

Well after 4 weeks of being up in the air, my truck is down and I can report back.

I treplaced my electric engine oil pressure transmitter and that did not fix my problem with the pressure being pegged out.
I purchased a new gage and that fixed the problem, or so I though.
After my truck finally be re-assembled following the brake and bearing job, I was able to drive it for about 25 miles or so on Sunday.
On my first leg of the trip, the oil pressure appeared to be o.k.
The truck sat with the engine off for about four hours.
On the return leg, I noticed that the oil pressure starting maxing out again although now it varys with engine RPM. At idle and hot it is about 45 psi and then at 50 MPH or so & 2400 RPM it goes up to 120 PSI. This obviously not a GOOD THING!
I want to put a reliable mechanical gage on the engine and drive it while comparing both readings against each other. I do not want to operate it for long like this, but I figure that another mile or two won't hurt for R & R.
I could plug a T-fitting into the block where the electric transmitter is attached but I was wondering if there is another area for a test gage for diagnostic purposes.
If there is a problem near or at the standard pressure port, I could perhaps eliminate some of the guess work down the road.
Any suggestions in this area would be greatly appreciated.
Now if after further research, the pressure is really doing what the electric system is displaying, then I have a problem. I have a lot of mechanical experinece with older jeeps, ect. but have never seen such a variation in pressure with as little as 1500 RPM (1000 high idle to 2500 on the road) but I have never torn into this big of an engine to date.
IF I DO have the blockage problem, what have some of you seen to cause this?
I will report back as I progess further with this issue to share my findings.
Thanks in advance, Jim
jimm1009@yahoo.com

 

[cranetruck]

The oil pressure regulator, located just below the turbo on the block is supposed to keep the pressure below about 70 psi. It is easy to remove and the unit can be checked out according to the TM procedure (spring lengths etc).

 

[avengeusa]

you need to add a regular t fitting to the oil passage way and install an elcheapo gage from autobone

you really need to get an accurate reading

 

[gbooth]

I also had a problem with the oil pressure gauge It would jump up 30psi and that was it. I installed a sunpro Retro gauge painted the rim OD as it has a black with white letters and white hand. Plumed it with copper line encased in rubber and it works great . If you did not know better you would not know. Heres a link to the gauge.

http://www.sunpro.com/product_detail.php?pid=16364

 

[ENCS_DEI]

The sending unit has to be grounded. check the threads are not sealed with teflon tape interfering with the ground. You may also want to make sure the engine is properly grounded (Driver side of engine rear inspection cover bolt to firewall).
Russ

 

[rosco]

Sometimes those electric guages, used on MV's, can drive you nuts.

I don't like "Cheap" guages! They tend to give you Cheap results. Mechanical guages work on the principal of using the berdan tube. That fails, you have a direct oil leak that can dump your oil out on the ground in a few minutes. That cute little blue guage would make me nervous, especially when its left in place, unattended.

Any body that does any amount of mechanical work needs a test guage. A reasonable source are the guages that are used on Oxy-acetelene tanks. You can pick & choose the Range of the guage, you need from them. Then I use a grease gun hose that is about 2 feet long, with a hand full of the appropriate bushings/reducers/bell reducers & tee's, to plumb in the test guage. Using a test guage, you can, at least know what your talking about, within a couple of lbs, at least.

Lee in Alaska

 

[Boatcarpenter]

"That cute little blue guage would make me nervous, especially when its left in place, unattended."
It's never left "unattended " when I'm driving the truck. It's about 8" in front of my right knee. highly visible. Any leakage and I will have a lap full of oil or notice 0 psi oil pressure. Very hard to miss.
BC

 

[lavarok]

jimm1009 - Did you ever figure out what was wrong?

I have the same exact problem in one of my trucks and already changed the sending unit. Mine came with no markings as well and my problem persists. Idle pressure reading at 52-57 PSI. I haven't driven it again yet since changing the sender, but I am sure it will peg out like yours. I am going to check the regulator and the grounding as suggest in this thread.

 

[SpyDad]

All, I know this is an older thread, but I am hoping someone can answer a quick question. I see a lot of concern in this thread about Op pegging out at 120psi... what if it is around 90 psi? Is this something I should be concerned about? How would I get it back down to around 70 psi?
Any help is appreciated.