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The '98 Ram we just purchased, seems to have low oil pressure, according to the gauge. With the engine off, the needle's pegged down below zero, which is normal. With the key in "On" position, it moves up to the zero, like it should. When I start it up, it reads at the white line just below 40psi (I'm guessing 20), and sits there, not moving at all, even with rpms. I'm not yet familiar with the Rams, but I thought that the pressure would increase with rpms. At least with every other vehicle that I've ever owned. But, I think that the psi should at least be 40 or higher.

I did my usual background check, as I do with all my vehicles, and checked the dealer service department visits, so that I know what work has been done in the past. Interesting enough, I found out that around '99, it was in for low oil pressure, and they finally replaced the heads to cure the flow problem. Our fear is that it may be acting up again, and that we may be screwed $ wise. No more warranty left. It only has 52K miles, which is why we bought it.

Just wondering what others have for running oil pressure, so we know if we have to look at it closer.

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Had some problems with my 96 V-10. Pressure was all over the place. Put on a new oil pressure sender and it fixed the problem. Hope this helps at all.

 

put a mechanical gauge on it and find out for sure if it's that low. I havent heard of heads causing a low oil pressure problem on any magnum engine and it doesnt sound right to me. the heads get their flow thru the push rods. the oil pressure sensor is back by the distributor and they have been known to go bad, causing funny readings on the guage. I've had to replace one on my old 318 in the Grand Cherokee and when I pulled it out, there was oil coming up thru the electrical connector so it wasnt holding pressure like it should.

 

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I figured I would do the sender swap first, since that's cheap and easiest to do. Gotta remember to get the special tool when I buy the sensor. Thanks.

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I agree with Steve about the heads causing the problem. There is no possible way for that to happen. As for the oil pressure sending unit, I don't recall there being a special tool on my 97 when I changed it. It just threads onto the block next to the distributor and has an 8 or 10 pin push/pull connector. I consulted my repair manual for this problem and the oil pressure should read 6psi at idle and 30-80psi @3000rpm. Personally, my engine runs between 35-45psi all of the time, even at high rpms. Another possibility is the oil line plug located in the vertical passage at the rear of the block between the oil to filter and oil from filter passages. It is mechanically seated and if improper mounting depth is present a dowel drift can be used to reseat it to correct dimensions. Accordingly, this can cause low, high, or erratic oil pressure signals to the sending unit. Unfortunately, a certified mechanic is probably the best solution to have this checked. I could see this being bad and the tech's that changed the heads out missing it or believing the heads weren't allowing proper oil flow, instead of it being improper flow to the heads. I really hope you understand all of this, tended to ramble a bit. Any questions, hope I can be of further help.
Todd

 

Actually Todd you will need the sensor socket, I needed one on my 318 in my Jeep Grand Cherokee. If the intake manifold is off, then you can easily get a wrench on it. here's 2 pics, 1 you cant even see the sensor and in the 2nd, it's right next to the distributor. the electrical connector is too big to get a socket over that's why you need the special socket... with the manifold on, you cant even get a wrench on it...

[IMG]local://upfiles/1508/5E77577230F14CD88D6C41BA80F0E8BF.jpg[/IMG]

[IMG]local://upfiles/1508/840ECE4EA0FB40A592C8DC370D8FE027.jpg[/IMG]

 

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Thanks for the replies guys... I'll try the sender unit first, and then look at the oil line plug if the problem persists.

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Money Pit -

Well, looks like Plan A didn't cure our low pressure problem, so we need to look at Plan B. Do you have any more info on that oil line plug?

I swapped ou the oil sender yesterday, and it still acts the same. It has 40+ psi at startup, and then drops down to about 20-25psi after the first mile or so of driving and just sits there for the rest of the drive.

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Sorry to hear the bad luck! I would think the next step would try an oil pump. The pan should be easy to get off. On my '98 5.9 I have 60 psi at idle and 80 crusing down the highway, in town or anytime it's off idle. I run Mobil 1 synthetic in everything except the trans which is ATF3. Best of luck in the repair!

 

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Yeah, an oil pump could be a next try to fix it. I swapped in Mobil 1 yesterday.

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