Only getting 4 pounds of oil pressure at idle. As soon as you give it a little throttle it goes up to normal pressure. Have tried two different aftermarket gauges and both show the same. When using the factory gauge it will show the idiot light until you give it throttle than it goes up to normal as well. Truck sounds and runs perfect. Any ideas. Also has fresh oil change and filter.

 

also has new sending unit

 

At what rpm? Adjust the idle up to 750-800 and it will probably solve it. If I idled my truck down to 550-600 it does the same as yours.

 

That is dangerously low though imo. only 4psi, that is hardly even flowing. What you need to do is hook a mechanical gauge right at the sending unit to verify if your problem is mechanical or electrical.

My mom's 4.7L durango started doing the same thing just it goes down to around 30psi at idle and then 60psi when on throttle and cruising. If you figure it out let us know.

 

How many miles on the engine? What viscosity oil, and is it regular oil or synthetic?
My guess, without knowing these, is that your bearing are getting worn and letting all the oil escape before building full pressure. One kinda cheap way of diagnosing is to hook a mechanical gauge straight to the same line as your idiot light runs off, at the back of the engine. Add 2 cans of STP oil treatment, it has the consistency of honey or molasses. It will thicken the oil. While running the engine at idle, dump the STP in, and watch your gauge. If it raises, usually means the internals of you engine are worn down to the point that at idle, your oil pump can't keep up with the volume of oil leaking out of your main bearings and rod bearings.

 

I would be very careful with this a friend of mine didn't take care of this when his 6.9 dropped down to 3 psi at idle and around 25 during driving and he ended up breaking a couple chunks off the block right around where the mains bolt in

 

Mine does the same, it stays in the normal area, though, but when driving, it rises quite a bit.

 

We put a mechanical gage on ours when we got it almost 2 years ago with 230,000 miles.

It has stayed pretty much the same since we got it and this post has me scared.

On cold startup it goes past 40. as well as when reved out.

After its warmed up it is under 10, but I never messed with it since I would see oil splashing at idle with the valve covers off?

Also I was wondering about the gage being t'd off, keeping the stock one working, and one of those cheaper kits with those crappy lines that seem to seep. I try not to tighten those down to tight so the nuts don't strip. Used plastic and copper lines and I cannot stop the slow collection of oil, don't know what I am doing wrong.

Also my pressures are relative to the pedal, so if I am just cruising it may only be in the 20's.

We have put less than 20,000 miles on it and it seems to run just as strong as when we got it?

With that being said what are the ranges we are looking for?

 

In my auto book for shool it says that most manufactures recomend a minimum of 10 psi for every 1,000 rpms. so at 2,000 rpm you would be looking for ~20 psi. i don't know if these numbers are different for diesels though.

 

Well, I am a school-trained diesel mechanic, but mostly experienced in over-the-road trucks and farm equipment. The only experience I have with these are my own 6.9's, but, I think most of the problem with low oil pressure at idle with these engines is the cooling jets that spray oil on the underside of the pistons. At idle, the pump just hasn't got the volume to keep the pressure up.
The 6.9 I have on the stand now had 150,000 on it, and it also had low oil pressure at idle. The main and rod bearings looked fine, no abnormal wear, and were replaced with standard sizes. Crank looked fine, so did camshaft. Everything that depends on oil for lube to keep it from seizing looked well within wear limits, but the previous owner said it idled with about 5 psi oil pressure.
I guess, in my experience, that I am not going to tear one down or sweat bullets if the oil pressure returns to normal as soon as it revs up. I am just going to use a good-quality higher viscosity oil to keep the parts lubed as best I can at lower rpm's, add something like STP, and not let it idle for lengthy periods.

 

4PSI well yeah its not ideal but okay for a high mileage IDI!. Remember these engines DO NOT depend on PSI but rather flow! The pumps will do over 12gpm at a good rpm. The engine is probably nearing the end of its service life and the tolerances are very large now.

 

When I got my 1987 6.9 a few years back the stock oil gage started out about the "N O" when starting cold. After it was warmed up it got almost to the bottom or the presure range. I also asked on this forum about low pressure and almost everybody said the same thing, "get a mechanical gage". I did and found out when cold I had about 50lbs and after warmed up I had 10/15lbs of pressure. One less problem to worry about All of the pressures are at idle.

 

I have around 17 at idle and at cruising speed I have between 35 and 40 when warmed up at cold I have around 30 at idle and 60 at cruising speed

 

I have 40 psi at idle on cold starts and about 15-20at warm idle. I run about 40-50 cruising down the road warmed up. This is where it is supposed to be. As the Gashog said it is flow instead of pressure

 

got the idle turned up and all seems to be good. Hope the internals are good as we will drive the truck till it dies.