oil pressure gauge (Page 1/1)
ausfiero123 JUN 09, 07:48 AM
Hi again,sorry about all the questions but being a new owner a few things keep popping up. I am assuming there is a simple fix for my issue, my oil gauge continuously flickers so is the issue the sender or the gauge? Generally it reads a fairly high pressure but seriously jumps around most of the time. Opinions please.....
82-T/A [At Work] JUN 09, 08:33 AM

quote
Originally posted by ausfiero123:

Hi again,sorry about all the questions but being a new owner a few things keep popping up. I am assuming there is a simple fix for my issue, my oil gauge continuously flickers so is the issue the sender or the gauge? Generally it reads a fairly high pressure but seriously jumps around most of the time. Opinions please.....




Does it jump around while you are driving, or does it also do it while your car is idling and sitting still?

I'm just wondering if there is a loose connection somewhere, either at the connector itself, or in back of the gauge cluster... that's my thought. Any chance you can post a video so that we can see?
theogre JUN 09, 03:05 PM
For oil pressure, always test w/ a "real" gauge to make sure the engine is happy...
V6, VIN-9, 30-45 PSIG
L4, VIN-R, 36-41 PSIG

Yes, "jumping" gauge or reads wrong can be:
The Gauge
The Sender
And/Or Just About anywhere else.

Fuel Temp and Oil Gauges are not simple meters. All have resistors "bolted" to the back that get dirty and other problems.
Gauges then go thru clips and more just to get power, ground and signal...
see http://www.fiero.nl/forum/Forum2/HTML/146784.html

Sender ground to engine etc and ground problems any in the car often affect them.

Note: If the oil sender is old type then replace w/ 88 sender and new plug.
New sender can fail but doesn't leak Oil like old type. use search.

------------------
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

ausfiero123 JUN 09, 04:43 PM
Will try to get a video of it but difficult when driving. From memory it just has a very small flicker when stopped and at idle but goes crazy when driving so will follow up the suggestions and see where we go. Will try to get a pic of the car for you also,just for interest sake. Thanks.
armos JUN 09, 07:51 PM
The twitchy oil pressure gauge is frequently caused by a bad oil pressure sender. Wiring could also do it but that's a lot less likely.

If you do anything with electronics then maybe you have some resistors around. You can unplug the sender and plug a known resistance into it's place to see if the gauge is reading correctly for that resistance.
I don't remember the exact scale but on a V6 with oil gauge on the center gauge pod, I recall it being close to 1psi/ohm. So 68-82ohms should read at the high end of the scale on the gauge.
If you try that experiment keep in mind what the current draw will be at ~12-14V - most common resistors will get hot and burn quickly. You can use multiple in parallel to mitigate that.
If the gauge works correctly with a resistor then the sender is faulty.

I converted my 86 to the later style sender shortly after I bought the car. In retrospect I wish I had tried using an 86 style at least once to see for myself how it would work out.
If you want to do the conversion to 88 style you need to replace the electrical connector. Wiring is compatible, just the plug is different.

If you buy an 88-style sender, get the ACDelco. Do not buy BWD. They're calibrated wrong, and will give incorrect low pressure readings at hot idle. Comparing with a mechanical gauge will confirm that they are wrong. Some of them read so low you will get a bogus oil warning light every time you stop at a light. The one I bought had a lifetime warranty so I went through 4 of them.

The quality of the Delcos isn't good either, I've had them fail multiple times, but at least the calibration is correct.

The above is for a V6 with an 88 style sender. I don't know if the 4cyl sender is different.
82-T/A [At Work] JUN 10, 11:52 AM

quote
Originally posted by armos:

The twitchy oil pressure gauge is frequently caused by a bad oil pressure sender. Wiring could also do it but that's a lot less likely.





It's been over a decade since I drove my 87 Fiero... and really, almost 20 years since it was something I drove every day, but reading this again, it totally is consistent with my experience as well.

My oil gauge would jump around erratically, rather than sit normally (and fluctuate slightly based on engine rpms). I ended up replacing the oil pressure sender, and that absolutely fixed it.

For those less affluent, that's basically the "sensor" that measures the oil pressure. It's located to the right of the engine, when looking at it from the back... e.g., the passenger side.

This guy:




Be careful when you remove it. It's likely really tight on there, and the only thing it's attached to is that little tube. You will absolutely need to put a wrench on that block below it, so you you make sure that when removing the sending unit, you do not bent and twist the tube and bracket off.

[This message has been edited by 82-T/A [At Work] (edited 06-10-2023).]