86 cj7 oil pressure sending unit / guage - JeepForum.com
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post #1 of 42 Old 04-02-2020, 08:13 PM Thread Starter
cj7jeepin
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86 cj7 oil pressure sending unit / guage

The original engine was the 4 banger . It has a 258 from a yj now. Finally got it running today after a lot of work wiring Howell tbi exhaust etc. the oil pressure pegs 80 in the run position but as soon as you start it it drops to 0 . Do I have no oil pressure or is somthing wrong? I grounded the the wire off of the sending unit and it jumps to 80. Thanks in advance

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post #2 of 42 Old 04-03-2020, 12:58 AM
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Sounds like the sensor is faulty. It is grounded at 0 pressure and then flakes out when it has any pressure. By grounding it you have verified the wiring. I sit possible you have a pressure switch and not a sender? The switch closes below 4psi and would give you these symptoms.

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post #3 of 42 Old 04-03-2020, 04:12 AM Thread Starter
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I was under the assumption I had both . It’s hard to see in this picture so let me know if I need to take a better one.
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post #4 of 42 Old 04-03-2020, 05:39 AM
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You could have a mismatched gauge and sending unit if you are using the sender that came on the engine and the original gauge.

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post #5 of 42 Old 04-03-2020, 05:49 AM Thread Starter
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I thought abt that after reading some posts. So I took the one off of the 4 banger and tried it and had nothing. No signal at all.
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post #6 of 42 Old 04-03-2020, 06:08 AM
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Have you thought about tossing all and going with a mechanical gauge? IMHO mechanical is more accurate and less expensive. I replaced my 45 year old electric gauge and sending unit with a mechanical for less than the cost of a new sender.

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post #7 of 42 Old 04-03-2020, 06:35 AM
John Strenk
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YJ oil pressure resistance :
PSI .................................................. .......................Ohms
0 .................................................. ............................1
40 .................................................. .......................... 37
80 .................................................. .......................... 89

CJ Oil Pressure resistance [2"]
PSI..................... Measured Ohms............................. spec chart ohms
0......................... 239.............................................. 227-257
5......................... 239............................................... 146-219
40....................... 108............................................... 83-123
80....................... 40................................................ 22-51

or

CJ Oil Pressure resistance [1"]
PSI..................... Measured Ohms............................. spec chart ohms
0-4................................................. .............................. open
33................................................ ................................ 20-32
63................................................ ................................ 13-25
90................................................ ................................. 9-17

(tip of the hat to Fjguercio for the chart)

So it's completely backwards for a CJ oil pressure gauge.

Yeah it won't work. Hopefully you haven't damaged your gauge.

More Oil pressure sending unit info:
https://www.jeepforum.com/forum/f8/c...-depth-920751/

or

This post actually has some part numbers:
https://www.jeepforum.com/forum/f8/c...essure-741622/


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post #8 of 42 Old 04-03-2020, 07:02 AM Thread Starter
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I ordered a sending unit for a Cj would that remedy the situation assuming the guage is still fine? Thanks for all the help
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post #9 of 42 Old 04-04-2020, 01:47 AM Thread Starter
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So I got the sending unit from o Reilly’s , I’ll have to double check the part number. Issue is that now I have a zero ohm reading when i check across the post to ground. But when the car is running I get a steady 40 psi at abt 2000 rpm (haven’t properly set up the Howell yet) . Does this sound correct?
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post #10 of 42 Old 04-04-2020, 09:10 AM
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Quote:
Originally Posted by bob4703 View Post
Have you thought about tossing all and going with a mechanical gauge? IMHO mechanical is more accurate and less expensive. I replaced my 45 year old electric gauge and sending unit with a mechanical for less than the cost of a new sender.
That's what I did. Simpler, and more accurate.
Mine is putting out 38 PSI at idle, and going up to almost 50 at road speed (I don't have a tach).
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post #11 of 42 Old 04-04-2020, 03:18 PM Thread Starter
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I’d rather keep the oem stuff if its all working. I just don’t understand why there is no resistance on the sender . The old one I had on the 4 cyl did the same thing but was dead and didn’t read anything while running. This one seems to read I just don’t know if it’s the right sender or accurate because I can’t get any resistance.
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post #12 of 42 Old 04-04-2020, 06:58 PM
John Strenk
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0 ohms or Infinite Ohms
Makes a difference
0 ohms is a dead short
Infinite ohms is an open.


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post #13 of 42 Old 04-05-2020, 03:11 AM
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Quote:
Originally Posted by cj7jeepin View Post
I’d rather keep the oem stuff if its all working.

And you should since they are unique to the CJ dash. You can always adapt a small liquid filled pressure gauge to the existing sending unit and pressure switch union fitting on the side of the block and have the best of both worlds.
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cjoffroad and weapon like this.

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post #14 of 42 Old 04-05-2020, 03:18 AM Thread Starter
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Honestly I’m not super great with multimeters , just enough to get by. I assume it’s infinite . It does not say 0 it has a 1 on the left side . Same as if I were touching nothing at all.
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post #15 of 42 Old 04-05-2020, 03:19 AM Thread Starter
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I double checked the guage tonight as well and it’s kinda surging between 40 and 50 psi at roughly 2000 rpms .
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