Low oil pressure at idle 93 Trooper

A few days ago I noticed that when at idle my oil pressure needle flutters just above 0 and the oil light flickers on and off. Once I'm on the gas the
pressure seems fine. This happens more often then not but it is a random thing. Oil levels are fine. As a mater of fact, I just added oil prior to noticing this problem.
What should I be looking at. Pressure sensor? Oil pump? Any other ideas?
--

Rob





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I noticed the same thing somewhat often on our 94 (but not the oil light coming on as you describe). I posted a message here about in the group and someone replied theirs did it all the time and they had stopped worrying about it. However, if you're getting the oil light flickering on too, could be something more serious...
Wesley

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"Robert R Kircher J" wrote: > A few days ago I noticed that when at idle my oil pressure > needle flutters > just above 0 and the oil light flickers on and off. Once I'm > on the gas the > pressure seems fine. This happens more often then not but it > is a random > thing. Oil levels are fine. As a mater of fact, I just added > oil prior to > noticing this problem. > > What should I be looking at. Pressure sensor? Oil pump? Any > other ideas? > > -- > > Rob
I used to own an 85 Isuzu 2.2 turbo diesel C223 engine in a Jackeroo. The engine being an old diesel it suffered from exactly the same problem and after checking with a capillary type gauge I noticed that the oil pressure at idle when cold used to be at 85 P.S.I. (which is a lot higher than any petrol engine that I have owned)and when hot at idle used to drop to as low as 10 P.S.I. sometimes even 5 P.S.I.
Once the engine revs were raised up the oil presssure then went up to about 45-60 when hot. So it was only ever a problem at idle. I have been told that this is a common thing that happens to old diesels and not to worry to much about it.
It is caused by wear in the big end bearings thus increasing the clearances between the con-rod and bearing. Due to the extra clearance the pump has trouble keeping up pressure and the fact that the turbo heats the oil more than normal wouldnt help either. But this only a problem at idle when the engine is under no load anyway.
I used to run a 15W/40 weight oil, but because of my problem tried using a straight 30 weight oil, but this actually made it a bit worse. My next step was going to be, trying a penrite oil 20W/60 which I have no dought would of fixed the problem. But I got rid of the car before I had a chance to find out.
However mine was never that bad that the temp light came on. They are normally set at around 3-5 P.S.I.
If I were you I would check the oil pressure with a capillary type gauge just to rule out a possible elctrical type fault. If your pressure comes reasonably high with this gauge when cold then you can probably rule out a problem with your oil pump and put down the pressure drop to increased clearances inside your engine.
I would also check if the idle speed is set high enough. If it is, it probably wouldnt hurt to bring it up about 150-200 R.P.M. anyway, which should raise your pressure by a bit at idle.
Just as an exercise - When turning off your engine switch it straight back to the ign positon and see how long it takes for you oil light to come back on. When cold it may take as long as 5-10 seconds. When hot it will come back on nearly straight away. On a newer engine even when hot it will still hold its pressure for about 3-5 seconds. Dont hold me to those time factors, I only used those times as an example.
I hope that this helps you out. In short it is perfectly normal expecially with old diesels. Let me know how you get on.
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<snip>

This sounds a bit goofy. This would be a problem if the sensor were located between the con-rod and the bearing, but it's not.
Just a thought.
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Not if you think the oil is in a pumped loop, where as any loose parts (gaps) will cause pressure drop in the system.

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"Robert R Kircher J" wrote: > A few days ago I noticed that when at idle my oil pressure > needle flutters > just above 0 and the oil light flickers on and off. Once I'm > on the gas the > pressure seems fine. This happens more often then not but it > is a random > thing. Oil levels are fine. As a mater of fact, I just added > oil prior to > noticing this problem. > > What should I be looking at. Pressure sensor? Oil pump? Any > other ideas? > > -- > > Rob
No Dollar Bill I have to agree with Thu.
The extra clearances created by wear in an engine do allow the oil to flow more easily through these "gaps" therefore creating a loss in backpressure which is in turn picked up by your pressure gauge/sender which is in the same loop.
As the engine heats up these clearances can become greater due to different rates of expansion of the different metals in the engine and as the oil heats up the viscocity can drop also also adding to the problem.
Also just because the pressure has dropped though, doesnt necessarily mean that your engine is not getting any oil to all the components. As the pressure drops the flow rate of the oil will increase (as long as the pressure drop is not due to a failing pump). Which means that the oil can actually flow around your engine faster than a newer engine with good clearances.
Believe me if the parts of your engine were not getting oil you would not get far at all!!
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