Low oil pressure on a 258 - Page 2 - JeepForum.com

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post #16 of 23 Old 11-15-2013, 10:35 AM
157jeep
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i had the same problem, no to low oil psi. on newly rebuilt, found i had forgoten to put the front oil galley plug in. got oil to lifters but no higher. plug in psi good

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post #17 of 23 Old 08-06-2016, 08:56 AM
MTJeepGuy
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I have a 1980 J10 which has 12,000mi on the rebuild. It ran 40-60 consistently until a few weeks ago. It now still runs 40-60psi cold and then drops to 20 when it warms up and then under load or on the highway (2000-3000rpms) it drops down to 15psi. As soon as I pull over and let it idle the pressure comes back up to 25-30psi. Any ideas? I don't believe the oil pump or pressure regulator valve were replaced in the rebuild but it has run good oil pressure until lately. The guys at my local mechanic shop said "No worries. Anything above 3psi is 'oil pressure' and that's all you need to keep running it." I am nervous about the new lack of consistency in oil pressure so I'm going to get a couple more opinions. I also own a jeep cherokee (1995) which has 235K on the Chrysler I6 and still runs consistent 40-60psi no matter the temp or how hard the engine is working. While I realize two totally different engines I'm not used to seeing that low oil pressure and after spending the money to rebuild the engine in the J10 I don't want to ruin it, so, I'm going to keep checking with folks. Any input folks might have on here would be appreciated. The oddest part of this for me is that the oil pressure stopped being consistent after about 11-12K miles on the rebuild and now runs higher oil pressure at warm idle than running down the highway at 3,000rpms warm. I HAVE replaced the sending unit and tested the wires from the sending unit to the instrument panel and gauges. That all checks out! Thanks!
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post #18 of 23 Old 08-06-2016, 09:55 AM
Spieg8
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Could be sign of an engine problem. Or it could be a screwy gauge/sending unit/wiring. I'd verify the pressure reading with another gauge (preferably a good mechanical gauge).

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post #19 of 23 Old 08-06-2016, 11:32 AM
LumpyGrits
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Cj

NEVER trust OEM Jeep oil psi, ele gauges.
If you really had the low psi the gauges sez you do. Your lifters would be 'talking' to you.
LG

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post #20 of 23 Old 08-06-2016, 12:13 PM
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Quote:
Originally Posted by LumpyGrits View Post
NEVER trust OEM Jeep oil psi, ele gauges.
If you really had the low psi the gauges sez you do. Your lifters would be 'talking' to you.
LG
I agree. Also, it's possible to get the wrong oil pressure sender for the OEM gauge. There were two styles and the wrong sender could scare the daylights out of you.

A sender giving you 68 ohms means 60lbs of pressure with one gauge, and 0 with the other. Verify first, then panic.

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post #21 of 23 Old 08-06-2016, 01:05 PM
LumpyGrits
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Cj

Even IF you have the correct 'sender'. It could very well be the gauge that's TU.
Also-A lot of these gauge issues can be traced to bad GND on the dash panel. Run a dedicated lead from the dash panel to the battery NEG(-).
LG

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post #22 of 23 Old 08-07-2016, 08:37 AM
keith460
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I had a similar problem with my rebuilt engine where the oil pressure would drop after reaching operating temperature. Found the problem being the new oil pump, Meling, was not machined flat like the original and required a gasket under the mounting surface. The original did not have one so I installed the new one without one too. That turned out to be the problem and had to drop the oil pan, remove the pump and install a gasket for the pump-to-block mounting surfaces. Cured my issue and now oil pressure is at 60psi when cold starting and then settles to about 20psi once things warm up.


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post #23 of 23 Old 08-07-2016, 12:59 PM
johnnykind
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Red face low oil pressure

Quote:
Originally Posted by 81cj7id View Post
I have a 1981 Jeep cj7. It has the 258 which was recently rebuilt. The problem is it only holds about ten pounds of oil pressure at idle. Is this right? A brand new oil pump was installed when it was rebuilt. I also get a tapping noise that sounds like valves/lifters. Any ideas? Thanks.
Had the same thing here is what happened to me, during the engine rebuild we missed a plug under the timing cover, I believe it was a 3/8 plug Allan head type...
everyone of those plugs that come in the rebuild kit have to go somewhere if you have some left over Figure out where they need to go !!!@

had low oil pressure for a week talked to all my mechanic buddys, put in a new high volume oil pump, still low pressure, did not want to blow up the new engine so we pulled the whole thing back out and started to take it back apart piece by piece till we found the hole for the missing plug put it back together, worked perfect !!!

Your problem may be different but that is what caused my low oil pressure, all the oil was going to the timing cover and not to the rest of the engine,
If your oil pump is working, and your GAUGE is working too, and you don't have any blocked passageways... try checking under the timing cover and make sure the correct plugs are in there...
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