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Old 06-03-2019, 08:00 PM   #1
tucsonjwt
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Oil Pressure Sending Unit

The oil pressure gauge on my 83 C20 454 has been reading high (~45 lbs) so I went looking for the sending unit and I think I found it above the oil pan on the driver's side toward the front of the engine. So, I have a few questions.

1. Is what I have in the photo actually the oil pressure sending unit?

2. There are only a couple strands of wire left attached to the unit, so is it possible to get deeper into the sending unit to splice into the wires coming out of it or are the wires sealed to the unit?

3. If I do replace the sending unit, will I lose any oil or can I replace the unit with the crankcase full of oil? Any tips for replacing that unit? It seems like there is only one single wire going to it - so is it grounded off the engine block?

Thanks
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Old 06-03-2019, 08:40 PM   #2
mongocanfly
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Re: Oil Pressure Sending Unit

Yep...that's it..
Not sure what you mean by splicing into wire coming out of it...it should have a terminal stud that the wiring harness plugs onto..
Wire attaches here...
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Old 06-03-2019, 10:37 PM   #3
tucsonjwt
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Re: Oil Pressure Sending Unit

Thanks for the information. I don't understand the threaded plug on the end shown in your picture and how it would involve an electrical plug. I don't see a blade for an electrical connection in your pic, and don't understand the mating threaded connection. Is there a piece I am missing?
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Old 06-03-2019, 10:49 PM   #4
mongocanfly
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Re: Oil Pressure Sending Unit

Ring terminal with a nut
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Old 06-04-2019, 09:26 AM   #5
tucsonjwt
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Re: Oil Pressure Sending Unit

Thanks. I got it now. I think I will try to carefully remove what is left of the wire and see if I can liberate that ring terminal without damaging the end of the sender. There appears to be a rubber boot on the end of the sender, so maybe I will find a ring terminal under that.
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Old 06-04-2019, 09:34 AM   #6
mongocanfly
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Re: Oil Pressure Sending Unit

Rubber boot would be common to protect threads and terminal...
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Old 06-04-2019, 04:57 PM   #7
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Re: Oil Pressure Sending Unit

Not sure on this one, but have seen similar setups work like spark plug wires. The wire connector simply is pressed on the end and held in place by spring pressure.

Also, the engine does serve as the ground for the sender current.

Sender probably has a little oil in it that will spill out when removed.

I would fix the electrical connections first before replacing the sender. Might get lucky and the problem is bad connections.
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Old 06-04-2019, 05:52 PM   #8
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Re: Oil Pressure Sending Unit

just replaced mine two weeks ago and it had a spade connector. the wiring harness had a plug with a boot on it like the OP pic.
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Old 06-05-2019, 07:35 PM   #9
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Re: Oil Pressure Sending Unit

My sending unit has a male spade type end for a 12 ga female quick connect. I replaced the wire up to the harness on the top of the engine with a 12 ga wire but I still have high oil pressure (maybe higher now ~ 48 lbs.) So, I will order a new sender and see what happens.

The original wire coming off the harness looked to be only about 18 ga, and the insulation was very hard from the desert heat + the big block engine heat. I had a very difficult time stripping off the insulation without shredding the wire, but I was able to get it soldered to a new 12 ga wire and put it inside a 1/4" wire loom.

I hope the new sender works or I guess the gauge is the only thing left to replace.
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Old 06-05-2019, 09:43 PM   #10
Wgesnerjr
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Re: Oil Pressure Sending Unit

Exactly like mine. I put mine in a year or so ago during the LS swap. It just quit two weeks ago. Quick replacement and I'm up and running again. Hope it lasts longer this time.
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Old 06-05-2019, 09:59 PM   #11
tucsonjwt
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Re: Oil Pressure Sending Unit

I have read elsewhere that a high pressure oil pump can cause these sending units to fail prematurely. I am surprised that an LS engine would use this old school one wire sender. I had to look around to get one of the AC Delco senders. Rock Auto had none - I am getting one from Summit, along with a side mount temp sender connector and lead to go with my new coolant temp sender which is reading too low. Oil pressure too high - coolant temp too low - between the two I should average out OK.
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Old 06-06-2019, 06:27 AM   #12
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Re: Oil Pressure Sending Unit

The LS uses a different style sender from the factory. To get the gauge to read correctly, I had to match the sender to the gauge.

My gauge reads about 55 at start up and 45 after warm up and at speed. I don't remember what brand the first sender was; could have been a cheap overseas unit. I would hope the new Standard sender could handle that kind of pressure.
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Old 06-06-2019, 08:51 PM   #13
tucsonjwt
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Re: Oil Pressure Sending Unit

Are you saying that your LS engine should have normal pressure of 45? The straight up center position on my oil pressure gauge is 30, so I am thinking that 30 is normal for my old 454. Am I correct? I am using 10W40 Castrol in this old beast, if that has anything to do with the oil pressure. The oil pressure does not seem to vary much whether at idle or at speed (I rarely get the truck over 55 mph, usually about 40 mph tops in town.) Thanks.

Last edited by tucsonjwt; 06-06-2019 at 09:15 PM.
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Old 06-06-2019, 11:48 PM   #14
Wgesnerjr
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Re: Oil Pressure Sending Unit

Not sure on your 454. I am running 10w40 for the summer, but may switch it back to 5w30. I think the pressure was lower with the 5w30.
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Old 06-07-2019, 02:40 PM   #15
tucsonjwt
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Re: Oil Pressure Sending Unit

I had a 63 SWC Corvette when I was a kid back in 1968-1969 which had a 327/300 which ran 40+ lbs. of oil pressure and everybody told me not to worry about high pressure - just be concerned about low pressure. I am anal about watching the gauges so high pressure always catches my eye.

BTW, the SWC is long gone - I sold it my first year in college - could not afford to keep it running and could not drive it in Michigan winters. I drove my second vehicle (1960 Chevy Carryall - think 2 door Suburban with barn doors and no back seat.) The Carryall was a great vehicle and more fun to drive than the SWC because I did not have to be concerned about it being stolen or banged up in a parking lot. 3 on the tree inline 6 cylinder and could go anywhere with just 2WD.
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