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Mikebaxter 09-08-2013 11:20 AM

Oil psi running high
My oil psi guage runs high when I start it and than when it warms it goes back down to about 15. It started spiking up to 40 psi when I hit the gas and than it drops down when I go in higher gears. I just replaced the oil two days ago and now it sits at around 20 when idling and goes to 60+ when I hit the gas.

walkerhoundvm 09-08-2013 11:40 AM

Give it time, it'll probably settle down as you break the oil in.

What weight oil did you replace with?

sarfu 09-08-2013 11:46 AM

Mine always does this, runs high when I first start it and takes awhile for it to drop down to about 20 PSI, PSI climbs as I apply the gas pedal.

Nereussailor 09-08-2013 11:52 AM

I run about 35 at idle on start up. It drops to about 20 when it warms up. At 2000 rpms, it runs about 60-65once warmed up. noyhing wrong with that.

Spieg8 09-08-2013 12:07 PM

I have no faith in electronic pressure gauges. Took turns replacing sending unit or gauge and would get inaccurate readings after only a few months. Put in a good mechanical gauge and have had no more problems since.

As previously stated, it's normal to get higher pressure readings when engine is cool and/or at higher RPM. If you are routinely seeing pressure dropping below 30 psi, you should think about replacing the pump and maybe some crank bearings (no motor lasts forever and eventually a complete rebuild will be required). In some cases you can get a little more pressure by switching to heavier weight oil (maybe you've already tried this, and that's why you get 60psi when motor is cold?). Most stock pumps have a relief valve set at around 60psi that prevents building pressure any higher. Before doing anything, I'd make sure you are getting accurate readings... maybe install a mechanical gauge temporarily (you can get a cheap one for about $20 and tape it to the steering column for a few days to see what's really going on).

CJ7KAHUNA 09-08-2013 12:13 PM

I've never trusted my oil pressure gauge. What mechanical gauge works well with the CJ / 258 set up?

LumpyGrits 09-08-2013 02:34 PM

What weight oil did you use? How many miles on the engine?
30psi+ swing from idle to run when hot, is normal.
High psi when cold at start up is normal.
AMC's OEM oil pressure gauge is CRAP. Get a mechanical gauge.


Mikebaxter 09-08-2013 03:56 PM

It just recently started running that high and that's what I think is weird because it always ran lower than that. I just put in 10w-30 but I'm sorry I forgot to mention that the motor was swapped to a scrambler motor with 20000 miles rebuilt. Like most cjs mine is a Frankenstein jeep and it's hard to remember all of the parts. I just thought it was suspicious that just one day it started doing that and along with all my other problems it may just be as simple as a broken guage.

LumpyGrits 09-08-2013 04:11 PM

Keep a log book of every thing you do to the Jeep, including PN's and at what mileage it was done.
Like I said---Don't trust the OEM gauge.

Spieg8 09-08-2013 05:36 PM


Originally Posted by CJ7KAHUNA (Post 15885318)
I've never trusted my oil pressure gauge. What mechanical gauge works well with the CJ / 258 set up?

I like these;

Any 2" (sometimes called 2-1/16" for the hole size) gauge will fit the factory CJ dash hole (just beware of the depth as there is not a lot of clearance behind the dash).

86cj74.2L 09-08-2013 06:57 PM

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This is mine kind of factory looking and totally mechanical.

82JeepCJ7 09-08-2013 11:05 PM

When I built my 304, I paid attention to all of the tolerances and the oil system. I am around 70psi on start up. After the engine is up to operating temperature, it settles in at around 22psi until I hit the throttle and then it jumps up to around 60psi.

WSS 09-09-2013 01:44 AM


Originally Posted by 86cj74.2L (Post 15886463)
This is mine kind of factory looking and totally mechanical.

X2! Sterwart Warner stuff is accurate and looks period correct


jeepdaddy2000 09-09-2013 06:28 AM

I'm going to be a bit of a dissenting voice here.
In my experience, a well built engine with a stock oil pump will hold a (relatively) steady pressure (usually about 40LBS) at both idle and service RPM's; hot as well as cold. This comes from the proper tolerances throughout the engine being tight enough to hold leakdown to a minimum. A stock pump will hold a steady pressure at idle when warm, with the bypass valve dumping the excess pressure at colder temps and higher RPM's.
Large fluctuations in pressure during cold operation and RPM changes usually points to some pressure leakage somewhere in the system, and 70LBS, as indicated above indicates a high pressure bypass spring has been installed. These can be bad on the cam and distributor gears due to the excessive force necessary to maintain that high of a pressure.
I am a big fan of good pressures at idle, since many of these engines are subjected to very low engine speeds during wheeling. A pressure below 30LBS at idle can become 5 or 6 LBS (or less) during a low speed lugging session in the rocks or other technical areas where the RPM's may be forced to drop well below norms (one of the reasons I run a high volume pump).

John Strenk 09-09-2013 07:05 AM

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I don't know, Ran my electrical and a mechanical pressure gauge side by side and both gave the same readings..
Maybe they just like me.

I would be more impressed with how many people have an oil pressure switch installed with a horn or alarm to warn of very low oil pressure.
just saying....

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