Oil Sending Unit Questions

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Oct 29, 2002 | 10:55 PM

Tourney3p0

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From: Warner Robins GA

Oil Sending Unit Questions

Hey everyone.

I have reason to believe that my oil sending unit is bad. When I start the car (it's an 88) my oil pressure is at 80.

I think the GM part number for replacement is #25036292. I'm going to call the local Chevy dealer tomorrow and get a price on this item, but it seems like I've seen them go for over 20 dollars (maybe much more). Is this right?

I took a trip over to Parts America Online since I have an Advance Auto Parts about a mile down the road, and I found a few different results. The most basic one is 6.99, made by GP Sorenson, and it goes up to 21.99 made by Niehoff Ignition. This is labeled as a switch with gauge. Will either of these work, or maybe a happy medium? Or should I just call the dealership and be done with it?

Also I'm wondering if the oil sending unit controls anything aside from the digital display itself. Basically, would there be any other possible adverse affects at all due to a bad sending unit?

I know I can change it out myself, so that shouldn't be an issue.

Thanks for your help.

Oct 30, 2002 | 05:08 AM

CentralCoaster

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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed

Re: Oil Sending Unit Questions (Tourney3p0)

Are you sure that 6.99 one is for a guage, not a switch? I priced them at Kragen, and bought the Niehoff. They did pull up a brand for really cheap like the one you mentioned. I don't think it can be used for a guage, it's more of an on/off voltage used to activate a dummy light, not a varying voltage. The Niehoff seems to work fine so far. It's actually a little longer than the original unit, so you can get a wrench on it (9/16"?) without removing the 2-pronged "oil pressure switch" (of course, you'll have to remove this anyways the first time to get the stock sending unit out.)

I'm assuming you're 88 is the same as my 85.

My oil pressure was showing ~8 psi with car off... and was usually high. The new unit seems to be working fine. My pressure is still reading over 65psi at cold cruise, 35-40 at hot idle, but I suppose that's a good thing...

Oct 30, 2002 | 07:24 PM

Tourney3p0

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From: Warner Robins GA

Re: Oil Sending Unit Questions (CentralCoaster)

I think you're right about it being the wrong unit. The next one up is $14.99, and the details are listed as "With Gauge; 1 Terminal; 1/8-27 Thread ". Is this what I need? That's part number OPS68, with the Niehoff counterpart going for $21.99 and listed as "Oil Pressure Switch - w/Gauge". I talked to a guy at work today and he said he was using the Sorensen unit with no problems.

My car also shows 8 psi with the car off. What does yours show now that you've replaced the sending unit?

Oct 30, 2002 | 07:37 PM

scorp508

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From: Boston, MA

Re: Oil Sending Unit Questions (Tourney3p0)

Quote:

I think the GM part number for replacement is #25036292.

14078954 is the P/N I used when I purchased a new Oil Pressure Sending Unit from Jeff Kopp for my '87.

Oct 30, 2002 | 07:52 PM

ZylaRace

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From: Norcross GA

Re: Oil Sending Unit Questions (scorp508)

The oil sending unit is a gauge and switch combo. It is not a signle wire connection. The switch will power the FPump if the primary circuit (EMC controlled) does not work.

Oct 31, 2002 | 04:06 AM

CentralCoaster

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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed

Re: Oil Sending Unit Questions (Tourney3p0)

Yeah, anything listed as "with guage" should be what you're looking for. The one you described is correct. Just be sure to yank it out of the box when you're in the store. It'll have one prong on it.

The original sending unit actually started to work at the last minute (0 psi when off) but I yanked it anyways. So far so good with the Niehoff unit, I get 0psi everytime I turn on the key before I start it. At first, it didn't seem to respond well to rpm changes, but it seems to be fine now. I guess I'm just used to the erratic readings from the other unit. I read on the forum last week where a guy had trouble with a few different brands before finally breaking down and buying the oem (delco?) unit from the dealer.

I'm pretty sure the 1-prong "oil pressure sending unit" is just for measuring oil pressure, and the 2-prong "oil pressure switch" is related to the fuel pump operation. They're two completely seperate sensors.

[Modified by CentralCoaster, 12:10 AM 10/31/2002]

Oct 31, 2002 | 09:16 AM

Tourney3p0

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From: Warner Robins GA

Re: Oil Sending Unit Questions (CentralCoaster)

That's exactly what I needed to know, thanks.

One other question though.. does the sending unit control anything else at all other than the gauge readout? I think I read that if it drops to a certain level (0 maybe?) then the car will turn off. Maybe that's why people tend to max out rather than hit zero when their units go bad? Anyway, are there any repercussions on the opposite end of the spectrum (ie, compensation due to too high of a pressure readout rather than too low)?

Thanks.

Oct 31, 2002 | 09:23 AM

vettmech

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From: Charleston, WV

Re: Oil Sending Unit Questions (CentralCoaster)

It supplies the fuel pump after about 2 seconds of engine run. The computer runs the pump for about 2 secs to prime the fuel system and that starts the car ........ then when it gets oil pressure the oil sending unit feeds the fuel pump. it's a safety thing so that if there is a wreck the engine quits and the fuel pump shuts down. :seeya