I know I saw this in a thread somewhere but haven't bothered to really search yet. Wanted to post this as more of a reference for others with the same problem to save some time/money tracking down the fix. Here's what's going on...
more than likely its your oil pressure sending unit.get a good brand replacement ( AC Declo ) and get the o-ring kit to keep water from getting in and causing it to bounce again. very easy fix. good luck
That's what I'm figuring it is too. Coulda swore I saw a recent post where it turned out to be something else tho. Regardless, the sending unit is gonna be the first thing I try.
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07:00 PM
ka4nkf Member
Posts: 3702 From: New Port Richey, FL USA Registered: May 99
It is your oil sending unit and if you want to fix it the correct here is how. You did not say what year you had, but I am betting you have a pre 88. If you will buy the 88 sending unit and buy the 88 connector and install on yours you will see a world of difference. I guess GM new the problem and changes the 88 model. Also some say get the rubber plug to keep the water out, this is not true because if you cut one open you will see where the problem is. It must leak a slight amount of oil and it gets all burning looking. The original hole in the sender was a vent to keep from creating a vacuum. With the weather proof connector thats on the sending unit it is not likely water gets into it. Switch to the 88 year model and you will like it. It is also cheaper. Don
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07:39 PM
Damien Member
Posts: 477 From: West Bend,WI Registered: Oct 2002
I'm assuming the 88 sending unit is a simple plug in and go other than the connector change. I did notice it was considerably cheaper as well. Is there anything I need to be forewarned about before I swap the sensor out for an 88 version?
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08:09 PM
Old Lar Member
Posts: 13798 From: Palm Bay, Florida Registered: Nov 1999
I'm assuming the 88 sending unit is a simple plug in and go other than the connector change. I did notice it was considerably cheaper as well. Is there anything I need to be forewarned about before I swap the sensor out for an 88 version?
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The 88 will screw right in and all you have to do is change the connector. Most auto parts stores have the connector. I did buy the special socket that is needed to screw it in, but the price of the socket still put me cheaper than the original one. the wires will connect the same as the old one. Don
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08:43 PM
May 6th, 2006
Damien Member
Posts: 477 From: West Bend,WI Registered: Oct 2002
Swapped the sensor out for an 88 and it seems to have presented an entirely new problem. As you saw in the video above, the old one just caused the guage to bounce around but the motion of the needle was smooth. With the new sensor in place the bouncing around is no more but the motion of the needle is far from smooth. It seems to skip throughout the entire range of the guage. I'm fairly certain it's wired correctly and it appears to be producing an accurate reading, higher pressure on startup and around 40ish when up to temp and idled down.... Any ideas?
Check C500... The oil sender wires run thru there. If that has problems gauge senders and other things can act up in wierd ways.
Check engine bay grounds as well. Bad grounds between engine battery and body will make gauges flip out.
Did you use anything on the threads? The sender has to ground thru the threads. They usually come with the correct sealer already applied. If they don't you have to use pipe dope, not teflon tape.
It's also possible you got a bad sender. Bad new parts happen.
------------------ Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should. (Jurasic Park)
I don't remember for sure the color of the wire but The gauge wire is brown and I think the black wire is fuel pump and the other striped wire is 12 volts.
looking at the guage -----------------------------------BRN
Check C500... The oil sender wires run thru there. If that has problems gauge senders and other things can act up in wierd ways.
Check engine bay grounds as well. Bad grounds between engine battery and body will make gauges flip out.
Did you use anything on the threads? The sender has to ground thru the threads. They usually come with the correct sealer already applied. If they don't you have to use pipe dope, not teflon tape.
It's also possible you got a bad sender. Bad new parts happen.
Everything was fine with the exception of the old sensor being bad. It read accurately but bounced around alot. The threads on the new one already had a sealer on them so I didn't use anything else. I put a glob of dielectric grease at the top of the plug to seal that part off but apparently I got some on the connector pins as well. Tried cleaning them out today but don't think I got it all.... I'm thinking it shouldn't affect it that badly, am I wrong? If it isn't that, then it's almost certainly a faulty sensor. Thanks for the help ogre.
Dielectric grease should not effect it at all, I would check your C-500 though, before buying a new sensor. Heres some Wiring Diagrams and Pinouts that may help:
