oil pressure sending unit question - JeepForum.com

 
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post #1 of 14 Old 08-21-2013, 10:03 AM Thread Starter
wsmutch
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oil pressure sending unit question

I decided to try getting my oil pressure gauge going. I'm looking at the sending unit, and I see a 3 prong connector. I can't find the matching connector or wiring that might go to it. There is one to to top. I get nothing at the gauge, no movement at all.

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post #2 of 14 Old 08-21-2013, 10:29 AM
WindKnot
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Look at my picture. The sender is the one on the left. There should be only one wire attached. For my year it is purple. On the right side is another sender dependent on oil pressure. For me it was an aftermarket electric fuel pump that will shut off the pump when the engine is stopped even though the ignition is still on. (Like for example if I ran into a tree or something.)

You have something similar but it's from the factory. Your Jeep is newer than mine. It maybe was a hookup for a computer or something emissions related, I don't know. But for the oil pressure gauge, you want to hook up to the sensor that looks like mine.


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post #3 of 14 Old 08-21-2013, 10:30 AM
gosupes
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That's a pressure switch, used for idiot lights, manifold heaters among other things. Three terminals, likely common, normally open and normally closed. Your pressure sensor is the round can right above the switch behind that bundle of wires. I think the sensor just uses a wiper arm across a resistive element. You can try using an ohmmeter from the terminal to a good ground and see if it changes with pressure changes. Or just say the hell with it and plumb in a mechanical gauge.

1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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post #4 of 14 Old 08-21-2013, 10:34 AM
LumpyGrits
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The sending unit(110%, OEM, POS)is on the left side of the pictures.
BTW, NEVER use Teflon tape on these, as they need a good ground(GND)for the electrical circuit.
LG

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post #5 of 14 Old 08-21-2013, 10:45 AM
WindKnot
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Mine works just fine with zero resistance. It was also just around one lap and not half the roll. the Teflon will tear if it's thin enough.

I'd rather be lost on the trails than found at home!

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post #6 of 14 Old 08-21-2013, 10:50 AM
LumpyGrits
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When I used the brass pipe, it cracked in a yr of Jeep'n
Went to a steel pipe, and no issues.
LG

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post #7 of 14 Old 08-21-2013, 11:20 AM Thread Starter
wsmutch
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So, the wire on to goes to the gauge and the three prong is not necessary to get a reading at the dash?
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post #8 of 14 Old 08-21-2013, 11:35 AM
LumpyGrits
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Correct
LG

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post #9 of 14 Old 08-21-2013, 04:25 PM
86cj74.2L
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I put a mechanical Stewart Warner Gauge in the CJ when the sending unit died.

With the copper hook up kit I bought it will last forever.
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post #10 of 14 Old 08-21-2013, 06:09 PM
LumpyGrits
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I did the same thing, after the second sending unit died while the Jeep was still in warranty.
LG

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post #11 of 14 Old 08-21-2013, 06:35 PM
keith460
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The three prong plug is for the Electric Choke Switch, but don't recall it being 3 prong as it is a more common 2 prong switch. It allows voltage to be applied for the coil of the Manifold Heater and carburetor Electric Choke.

If you are worried about what your actual oil pressure is and find that the OEM gauge is not accurate or functioning properly, do yourself a favor and add a small liquid filled pressure gauge to the side of the engine block so you can know at a glance whether oil pressure is present and at what the current pressure is at.

I used a small liquid filled pressure gauge that I bought from McMaster-Carr.com and added a 1/8 NPT thread to the existing pipe union for the Oil Pressure Sending Unit and Choke Switch.









The gauge in the picture is not liquid filled as it was changed out shortly after taken the photo.

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post #12 of 14 Old 08-21-2013, 06:59 PM
LumpyGrits
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Hey Keith, nice idea!
BTW, why don't you run that battery gnd to the top mounting bolt of the starter. Nut'n but good when you do.
LG

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post #13 of 14 Old 09-07-2013, 07:20 PM
70worm
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Can someone tell me how the wires hook up on the back of the gauge?
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post #14 of 14 Old 09-07-2013, 08:39 PM
titomars
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Quote:
Originally Posted by 70worm View Post
Can someone tell me how the wires hook up on the back of the gauge?
Red wire to positive terminal
Purple to neg or to sender
Orange for gauge light

1981 Jeep CJ7 4.0 HO, AX-15, D300, D30, D44, SOA
1977 Chevrolet C/10 step side 454 TH400 3.73 posi
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