Oil Pressure/Temp Gauge Questions - JeepForum.com
 
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post #1 of 12 Old 10-25-2021, 04:03 PM Thread Starter
jeffmcelwee
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Oil Pressure/Temp Gauge Questions

The last feller that had my Jeep (75 CJ5, 304 T15) disconnected the majority of plugs and sensors so I'm in the process of reconnecting or replacing everything. After taking the dash off today I have a few questions.

The coolant temp switch was missing in the thermostat housing. I got a new housing and switch (switch doesn't fit of course) but the wire to the switch seems to be missing. After taking the speedo cluster off I noticed that only 1 wire was connected and there's a bare terminal. Not sure if this is normal or not.

After looking at the oil pressure gauge I noticed the copper wire that I didn't know it's purpose was actually connected to that gauge. I saw on the block next to where the thermostat housing is was plugged like my old thermostat housing and I'm assuming that's where the oil pressure gauge is supposed to connect, but I don't have a basis for that.

I'm not sure if I'm correct about any of this so I'm hoping you guys can help!

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post #2 of 12 Old 10-25-2021, 06:08 PM
254Triple
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On my 72 304 , The brass plug shown is where I put the electrical sender for temp gauge, and I also have a mechanical water temp gauge and i put the sender in the thermostat housing. On the passenger side of engine up front just above the oil filter, I had a fitting on the housing where the oil pressure sender goes. It was about a 45 degree fitting so you can aim it as needed to hookup your copper line. Hope that helps
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post #3 of 12 Old 10-25-2021, 06:37 PM Thread Starter
jeffmcelwee
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Awesome thanks! This is a total noob question but how does the wire connect to the sender? I’ve been an XJ guy for years so all of this older CJ stuff is still fairly new to me!
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Originally Posted by 254Triple View Post
On my 72 304 , The brass plug shown is where I put the electrical sender for temp gauge, and I also have a mechanical water temp gauge and i put the sender in the thermostat housing. On the passenger side of engine up front just above the oil filter, I had a fitting on the housing where the oil pressure sender goes. It was about a 45 degree fitting so you can aim it as needed to hookup your copper line. Hope that helps
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post #4 of 12 Old 10-25-2021, 06:58 PM
Girth83
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Quote:
Originally Posted by jeffmcelwee View Post
Awesome thanks! This is a total noob question but how does the wire connect to the sender? Iíve been an XJ guy for years so all of this older CJ stuff is still fairly new to me!

I've got a 258, and my CJ5 is a bit newer being an '82, but I'd imagine that part is the same? The wire has a little rubber boot at the end, shaped so the connection is 90* to the wire, if that description makes sense. It's terminal inside the boot is like the female side of a "bullet" terminal..... slides right on over the threaded stud on the sender. I just squeezed mine a tiny bit with my crimpers yesterday, to make sure it fit snugly over that threaded stud.
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post #5 of 12 Old 10-25-2021, 07:46 PM
254Triple
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Those 2 wires in your pic by the brass plug, the large red one probably is for your coil+, where does that brown one terminate now? I would think the factory wire for your water temp sender should be very close to these wires if not the brown one? Maybe look down along the runner of your intake and see if you have a "dangler" with the 90 degree boot on it that Girth mentioned. I had to go an entirely new painless wiring harness so I don't know the factory color of the WT gauge sender wire. It is also possible that the wire could be hanging off the back of the engine. I bet it is there, just need a good flashlight and close checking. Image is from the 72 TSM and shows it to be Bluw w/Yellow tracer.
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Last edited by 254Triple; 10-25-2021 at 07:58 PM.
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post #6 of 12 Old 10-25-2021, 08:15 PM
bob4703
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I may have sent this link to you in another post but here it is https://oljeep.com/edge_74_tsm.html . There may be a slight difference between the 74 and 75 models but not much. If it doesn't look right look at the TSM for 76 https://oljeep.com/edge_76_tsm.html . 75 is a transition year so later production models may be more 76 than early ones. Between the two you should find any thing you need.

You have a single wire from the sending unit to the temp gauge and one from the oil pressure sending unit to the oil pressure gage. I spliced a female connector on the end of the wire to the oil pressure sending unit and slipped it on. I used a round connector to the water temp sending unit and fastened it with two nuts. You need to take the thermostat housing and sending unit to a parts store. Tell the counter man you need to go from here to there and he'll get what you need. all you need is a reducer to make it fit. While you have everything unhooked it would be the time to convert to a mechanical oil pressure gauge. They are less expensive and work better. Either my gauge or or my sender was feeding back to ground and killing the battery and it made the reading off.

Good luck.

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post #7 of 12 Old 10-25-2021, 09:11 PM Thread Starter
jeffmcelwee
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Ahhhhh the brown wire is the one! It has been spliced with 2 other wires so I'll clean that up a bit this week. I need to get in there with a flashlight and just stare for an hour to take it all in. My eyes are still trained to a 4.0! Looks like I did get the proper temp sensor, it wasn't in the place I suspected.
Quote:
Originally Posted by 254Triple View Post
Those 2 wires in your pic by the brass plug, the large red one probably is for your coil+, where does that brown one terminate now? I would think the factory wire for your water temp sender should be very close to these wires if not the brown one? Maybe look down along the runner of your intake and see if you have a "dangler" with the 90 degree boot on it that Girth mentioned. I had to go an entirely new painless wiring harness so I don't know the factory color of the WT gauge sender wire. It is also possible that the wire could be hanging off the back of the engine. I bet it is there, just need a good flashlight and close checking. Image is from the 72 TSM and shows it to be Bluw w/Yellow tracer.
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post #8 of 12 Old 10-25-2021, 09:14 PM Thread Starter
jeffmcelwee
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Looking more into the oil pressure unit location, would this plug by the oil filter be where the switch goes (pic 1)?

And since I have the copper line already run to the gauge, do I need an actual sending unit like the one in pic 2?
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Last edited by jeffmcelwee; 10-25-2021 at 09:24 PM. Reason: additional info
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post #9 of 12 Old 10-25-2021, 09:32 PM Thread Starter
jeffmcelwee
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That's a huge help and I bookmarked both pages this time!
Quote:
Originally Posted by bob4703 View Post
I may have sent this link to you in another post but here it is https://oljeep.com/edge_74_tsm.html . There may be a slight difference between the 74 and 75 models but not much. If it doesn't look right look at the TSM for 76 https://oljeep.com/edge_76_tsm.html . 75 is a transition year so later production models may be more 76 than early ones. Between the two you should find any thing you need.

You have a single wire from the sending unit to the temp gauge and one from the oil pressure sending unit to the oil pressure gage. I spliced a female connector on the end of the wire to the oil pressure sending unit and slipped it on. I used a round connector to the water temp sending unit and fastened it with two nuts. You need to take the thermostat housing and sending unit to a parts store. Tell the counter man you need to go from here to there and he'll get what you need. all you need is a reducer to make it fit. While you have everything unhooked it would be the time to convert to a mechanical oil pressure gauge. They are less expensive and work better. Either my gauge or or my sender was feeding back to ground and killing the battery and it made the reading off.

Good luck.
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post #10 of 12 Old 10-26-2021, 04:59 AM
John Strenk
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Make sure you know the difference when talking sensor or switch.

Oil pressure had both, switch for the electric choke if you had one and a pressure sensor for the gauge. If you are running a mechanical oil pressure gauge then you don't need the electronic sensor.
the 4.2 also used the oil pressure switch to control the manifold heater on the 4.2. I don't think there was ever an electronic manifold heater on the 304.

I don't think a temp switch was used on the 304. as far as I recall, it was only used on the computerized 4.2 and it ran to the computer. There was also one used for the manifold heater on the 4.2


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post #11 of 12 Old 10-26-2021, 03:48 PM
254Triple
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That shiny brass plug in your Pic1 is where your 1/8" copper line to mechanical oil gauge would go. You would need the 1/8" pipe to 1/8" tubing brass fitting. Tighten it in the block with thread sealer, don't go gorilla on it, just snug. Then you can take your copper line with the nut/Ferrel and attach to this fitting. Start it up and check for any leaks. You don't want one there as it will make a mess in a hurry. Make sure you route it so it is not rubbing or getting vibration from the engine.
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post #12 of 12 Old 10-27-2021, 09:03 PM Thread Starter
jeffmcelwee
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Thanks! I’ll report back when I get a chance to slap it on
Quote:
Originally Posted by 254Triple View Post
That shiny brass plug in your Pic1 is where your 1/8" copper line to mechanical oil gauge would go. You would need the 1/8" pipe to 1/8" tubing brass fitting. Tighten it in the block with thread sealer, don't go gorilla on it, just snug. Then you can take your copper line with the nut/Ferrel and attach to this fitting. Start it up and check for any leaks. You don't want one there as it will make a mess in a hurry. Make sure you route it so it is not rubbing or getting vibration from the engine.
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