Pinned Oil pressure Gauge (Page 2/3)
85GT556 APR 27, 05:52 PM
Great info.in this thread.I was having the same problem and just tested mine. It is a bad sending unit. Thanks everyone.
OneSlowFiero APR 30, 10:46 PM
Very informative thank you very much. The oil pressure gauge hasnt worked properly since the day I bought the car. I will order a new sending unit from rock auto. Even if the unlikely happens and it isn't the sending unit, it sounds like it is good to have one on hand. Heck I might even buy 2!

Thank you for all your help!
-Josh
newguy22 AUG 04, 05:31 PM

Hi Everyone,

I just upgraded my 87 v6 to the 88 oil sending unit following the instructions on the Ogre's Cave Fiero site. The Car is running fine, but my gauge which had been bouncing around is not pinned to the far right. Car on or off. I pulled the tan (center) line from the sender and grounded it as described in the post below and my gauge went to zero. Sounds like this is a bad sending unit...but it is a brand new AC Delco part. #1808A. Any ideas? I am actually worse off than I had been. LOL.

Thanks, Bill

quote
Originally posted by phonedawgz:

The gauge technology that GM used in the 80's put two electromagnetic fields against each other. They did that instead of an electromagnet against a spring. After time the spring will weaken making a spring/electromagnet gauge inaccurate.

So when the key is off, what happens to the needle has no meaning at all.

A simple test of your oil pressure gauge/sending unit. Unplug the connector from the sending unit. On 85-87 that means squeezing the ring to make it more circular and then pulling up. With the proper squeeze it will pull up fairly easy. Now turn the key on, but leave the engine off. The needle of the oil pressure gauge should read far past high right. Now take a straightened paperclip and insert it into the CENTER pin of the three and hold that against ground. The needle should move to 0 PSI. If you wish to make a third test you can take a 90 ohm 1/4 or 1/2 watt resistor (RadioShack $0.99) and insert it into the middle pin and ground it. With the 90 ohm resistor the needle should read full oil pressure, but not past full.

If your gauge reads what it should for tests 1 & 2, but it doesn't work correctly connected to the sending unit, your most likely problem is a bad sending unit. If your gauge reads low but at some pressure just jumps to full high, your problem most likely is a bad sending unit. That jump-failure is common with the 85-88 sending units.

Rock Auto has some reasonably priced sending units at $12.71 + shipping. Make sure your replacement sending unit looks like the one in your car or it won't fit on the electrical connector. Price check this before buying local. Some stores charge over $50 for this.

Note also - You must use a wrench on the metal part of the base, not that big looking plastic nut thing.

Oil pressure sender/switch for 85-87 Fieros


You can also replace the 85-87 sending unit with an 88 sending unit. You have to also purchase the wire connector and splice it onto your existing engine wiring harness.
johnyrottin NOV 17, 11:39 AM

quote
Originally posted by phonedawgz:

Note also - You must use a wrench on the metal part of the base, not that big looking plastic nut thing.




What would happen if you tightened on the plastic "nut"?
cybermars JUN 29, 03:42 AM
testing
cybermars JUN 29, 03:55 AM
Here is a little trick I figured out by accident. Pull the fuse listed gauges on the interior fuse box. if your volt meter stopped working and your oil pressure gauge now works. and If you have changed both your sender and gauge set like I have, you can you can pretty much bet that you are a proud owner of a melted wire.
PontiacTate SEP 25, 03:31 PM
Where would the melted wire be?
theogre SEP 26, 01:02 AM

quote
Originally posted by phonedawgz:

For a while the only available 85-87 senders were all in that $50 range. It was cheaper to replace the sender AND purchase the connector rather than just replace the old sender. With these lower priced ones on RockAuto that is no longer the case.

The other thing is the 88+ senders do seem to be more reliable than the earlier ones.

Better reason... Type used for 88 and up won't leak pressurize oil and dump all oil on highway because doesn't have leak problem when they fail.

See my Cave, Oil Sensor for install

How 88 units are made:
https://www.youtube.com/watch?v=OWrj6A3-_Os
http://www.airtexve.com/sft...it_sens_bulletin.pdf

88 just have a longer plastic to fit same high as older units but otherwise is same as short ones shown.

88 need 27mm Wrench for most but many types can work depending just where.

------------------
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.
(Jurassic Park)

The Ogre's Fiero Cave

centervilledon MAY 18, 09:00 PM
I have a dumb question as I am looking into what it would entail to get my oil pressure gauge working on my "85 GT 2.8 . Just where is the oil pressure sending unit? From what I gather, from reading theses posts, that if you take off the sender connector and short the middle pin to the block with the key on (motor off) the needle may move to zero. This would mean the sending unit is toast right? My oil pressure gauge needle moves to the center, around 40, when I turn the key on and with the motor off . As soon as the motor starts it goes all the right as far as the needle can go. Any thoughts? Centervilledon
AVaill6 OCT 12, 09:07 AM
I am having a similar issue with my 85 SE. pressure switch was leaking but worked, so I replaced it with a duralast one and now my gauge reads maxed when running. Don't know if I put the wrong one in but it wasn't the same style as the oem.