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I've searched a bit and found some threads discussing this but not any that quite answered my issue. So forgive me if there's one out there and I missed it. Also if y'all prefer me to resurrect and old thread instead of a new one, my apologies.

 

So here's my situation...

(I'm adding a bit of history to be sure I'm detailed for y'all)

First I switched out the P.O.S. plastic valve cover with an aluminum one I snagged off a 4 banger XJ. Got the correct gasket and everything went well with the install. I did an oil change 10w30 Synthetic. I immediately noticed a loud tap on the top end just as I turned it over. Only a second, then gone. I thought it may be something with he fit. I asked A buddy and he said it just sounded like it took an extra second for the oil to catch up. So I changed the oil with Rotella 5w40 synthetic and the tap disappeared :applause:...

 

And now to the oil pressure...

I swapped out my 89 pioneer dummy light cluster with a 90 XJ so I could finally get a temp, tach, and oil pressure reading. That also went relatively smoothly. I purchased (I believe) the correct switch for the pressure part #ECH OP6638 and swapped it with the old dummy sensor. 

My oil pressure read real high. No, not because the switch wasn't connected properly (I saw the spike to max b4 I had the switch installed). It was reading nearly 80 at startup and went down to 65~ at idle. Note: this was actually before I changed to the rotella t6. After the oil change it was ready maybe 70-75 at start up and around 55-60 at idle. When I accelerate its at 65-70.

I actually was able to swap the switch for a new one at Napa expecting/hoping the switch was faulty. No luck. Same reading.

 

I have a buddy that has a mech pressure gauge tester. To my delight, the gauge read 48-50 at idle and 60 when I gave it some gas. I was relieved to find out that my gauge runs 10 or so high. However that still seems a bit high, right?

 

So after ready elsewhere it would seem that its above normal. But I wasn't sure if it was maybe any different with the 2.5L's. Maybe higher pressure with the smaller engine? IDK

Would the gauges or switches read different in a 2.5L than a 4.0?

 

Thanks in advance for your help!

 

Oh and just to mention. I just broke 35k on this guy. Farm truck with low miles when I got it and it seems to be sealed up real well. No leaks that I can tell...

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remember your oil pressure switch works off ground. If you have a bad engine ground it will read high. disconnect the wire and start it up, it will go all the way to the right. I bet you either have a bad ground on the engine. either that or the line that go's to the gauge is not up to par. 

 

To check if your gauge is good, ground out the line that plugs to oil pressure switch. it should go the left when you turn the engine on, if it does not you may have a switch that has bad diodes

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Factory spec for oil pressure is 13 psi minimum at 750 RPM idle, and something like 35 to 75 psi above 1600 RPM. (Warm)

 

What I've observed is that (with the exception of very high-miles engines) they usually idle at around 25 psi and run 50 to 55 psi at 60 to 65 MPH. That's with 10W30 oil. Heavier oil will result in higher pressures.

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On 3/16/2018 at 5:36 PM, Eagle said:

Factory spec for oil pressure is 13 psi minimum at 750 RPM idle, and something like 35 to 75 psi above 1600 RPM. (Warm)

 

What I've observed is that (with the exception of very high-miles engines) they usually idle at around 25 psi and run 50 to 55 psi at 60 to 65 MPH. That's with 10W30 oil. Heavier oil will result in higher pressures.

So by your specs/observations I'm running high. What should I do?

 

'preciate your input, Eagle

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Those are very good numbers for an old engine. Above average, but your engine has low mileage and I would not be concerned. Was the idle number with the engine cool or hot? Oil pressure will drop as the oil warms. If it drops a lot when warm that's bad, but it will drop no matter what. 

 

My 91 with 175k miles has roughly 55 at cool idle, 35 or so at warm idle, and 55-60 with the engine under load. Hard acceleration at high RPM will make it jump to 65 or so. 

 

Trust the mechanical gauge over the dash gauge. Those aftermarket senders are often very inaccurate. Mopar senders are highly suggested. 

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On 3/16/2018 at 12:19 PM, SMPLTN said:

It was reading nearly 80 at startup and went down to 65~ at idle. Note: this was actually before I changed to the rotella t6. After the oil change it was ready maybe 70-75 at start up and around 55-60 at idle. When I accelerate its at 65-70.

I actually was able to swap the switch for a new one at Napa expecting/hoping the switch was faulty. No luck. Same reading.

 

I have a buddy that has a mech pressure gauge tester. To my delight, the gauge read 48-50 at idle and 60 when I gave it some gas. I was relieved to find out that my gauge runs 10 or so high. However that still seems a bit high, right?

 

Get a regulation Mopar oil pressure sensor and your dash gauge will read actual pressure. Not one from NAPA, Autozone, or any of the other aftermarket junk. The correct Mopar p/n for your truck is 53005218, about $25 on Ebay. Then your dash gauge might even agree with your buddy's mechanical oil pressure gauge  if it's calibrated correctly.

 

My stroker has read ~70psi cruising and ~25 psi at idle for years and I'm happy with it.

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And always use this simple rule....oil pressure is like money in your wallet or your wife/girlfriends boobs.......your never look at either of those and say " that's too much".....IMHO

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