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post #1 of (permalink) Old 10-02-1999, 04:46 PM
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Oil gauge Problems

Anyone else have problems with their factory oil gauge? At idle I'm at about 50psi, and giving it a little gas makes it jump to 75 psi. No engine problems at all, so I figure the gauge is just off. How can I fix this?


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post #2 of (permalink) Old 10-02-1999, 08:16 PM
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Re: Oil gauge Problems

How about a little more info? Is it 50psi cold idle ...... or all the time ( it should be less when hot - same with the high end pressure ). After you give it a little gas does it hang up at the higher pressure or return to the lower one? What weight oil are you using? What year and model (so that someone here knows what type of sending unit you have - electric - mechanical - electronic - etc.) with what engine? Is it an OEM gauge or after market?
I have a high volume oil pump ..... and even when the motor is cold I only get to about 58 psi ..... that's what my pressure relief appears to allow ...... I may go a little above that if I hit highway speeds before being warm ..... but 75psi seems a little on the high side to me ......

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post #3 of (permalink) Old 10-02-1999, 09:13 PM
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Re: Oil gauge Problems

MIne did that just before it quit working all together.


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post #4 of (permalink) Old 10-02-1999, 09:14 PM
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Re: Oil gauge Problems

I have the same deal. My Oil gauge starts out at low, but while driving it jumps all over. At a stop on a level surface is the only way to get a semi-accuratte reading.


post #5 of (permalink) Old 10-03-1999, 12:02 AM
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post #6 of (permalink) Old 10-03-1999, 09:14 AM
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Re: Oil gauge Problems

[img]/wwwthreads_images/icons/wink.gif[/img] I see from Grif's profile that both of his Jeeps are 93s. That means the 4.0, and usually they are pretty consistent on oil pressure...at least mine is....not over 50, and warm idle at about 25. You can certainly see the Chrysler influence in the oiling system over the early AMC engines. Chryslers have always had stellar oil pressure. I don't trust the senders all that much, and before I put the ranch up for auction I always check that. It's a lot easier than rollin' in a set of bearings. [img]/wwwthreads_images/icons/crazy.gif[/img] I always like to try the 98 cent solution first.....just a habit...that's saved me thousands of dollars and tons of grief. [img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/wink.gif[/img]

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post #7 of (permalink) Old 10-03-1999, 09:27 AM
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Re: Oil gauge Problems

my wife's CJ-8 had oil pressure that changed with RPM and engine temp. (also had some electrical needle spikes) it slowly got worse (more erratic/extreme readings) i didn't believe it was the engine, so i replaced the factory electrical guage and sender with a mechanical guage and tubing, now my oil pressure is more stable, i believe it's also more accurate.

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post #8 of (permalink) Old 10-06-1999, 10:50 AM
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Re: Oil gauge Problems

Oil Pressure gauge S terminal - Purple wire from sender
Oil Pressure gauge middle terminal - Black wire (Ground)
Oil Pressure gauge right terminal - Red wire (Ignition-on hot 12v)

The oil pressure sending unit is on the engine block and looks like a small 2 X 3 inch filter with one terminal. There may be another sender plumbed in the same area that has two connectors. It is an oil pressure switch that is supposed to close below 4 psi to activate a dash warning light in some speedometer clusters.

To be sure the problem is not the gauge, you can momentarily short the wire from the output of the Sender to ground. If there is no resistance, your gauge should read 80 psi. DO NOT hold it for long in this position. If the needle does not move from zero psi then, either the wiring (open circuit) or the gauge is bad. If it does move, the sender unit is bad.

It is very common for the sending units used with the 258 and 232 engines to be inaccurate. Make sure you have a good connection to the sending unit.

It is easiest to test the sending unit by temporarily plumbing in a good mechanical gauge.

Pressure (PSI) Resistance (ohms)
0 234-246
20 149-157
40 100.5-105.5
60 65-69
80 32.5-34.5

Jeep CJ Gauge & Sender Diagnostics
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[img]/wwwthreads_images/icons/crazy.gif[/img]<font color=purple> It's a JEEP thing!</font color=purple> <font color=red>1985 CJ7 </font color=red>[img]/wwwthreads_images/icons/crazy.gif[/img]
post #9 of (permalink) Old 10-06-1999, 11:24 AM
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Re: Oil gauge Problems

I love getting on on the 'ol "oil pressure reading" discussion.

My opinion is that electric gauges aren't accurate. If it reads anything, you have pressure. If it reads nothing, you may have pressure. The best way to check is either replace it with a mechanical, or buy a cheap mechanical for $10.00 and hook it up temporarily just to see if you have pressure.

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post #10 of (permalink) Old 10-06-1999, 11:37 AM
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Re: Oil gauge Problems

I'd have to agree with LEVE. My experience has been the same. My idle pressure is just under 20 lbs with a new oil pressure sending unit. Altho, it doesnt get much higher than about 25 lbs at highway speeds and I'm running 35" tires with 4.10s... so I think that's about right. I do, however, have higher oil pressure at startup....somewhere in the range of 35 - 40 lbs.

That's been my experience....

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