Just as the topic says...I bought a new sending unit thinking that was it...I know that the gauge is good because I just finished installing Tom's digital dash...before I did the swap my old analog gauge was also reading max pressure.
Anyone have the same thing happen and what was the fix?
I'm thinking direct short to ground or is it a open circuit?
A lack of ground can cause a pegged gauge. Whenever I've unplugged the harness from the sending unit, the gauge pings full right. Don't put teflon tape on the threads of the sending unit.
I don't believe teflon tape is causing your issue because GM used a sealer to prevent leaks.
But there is an easy way to find out if that is the problem. Run a jumper wire from the sender's body to a good exterior ground like the block or a bracket. If the gauge works then it is the sender's ground.
My thinking is that there is a wire to the gauge going to ground.
Mine pegs when I first start the car but goes down to normal oil pressure after about 10-15 minutes of driving. Was never able to solve the issue. Interestingly, I had recently changed the aux gauge pkg only because the housing had major cracks, which made the whole thing wobble a bit. The previous gauges I had in there did not have this symptom. Because my oil pressure goes back to "normal" after 15 minutes of driving, I have not pursued the problem. Kit
[This message has been edited by Kitskaboodle (edited 01-07-2016).]
I don't believe teflon tape is causing your issue because GM used a sealer to prevent leaks.
But there is an easy way to find out if that is the problem. Run a jumper wire from the sender's body to a good exterior ground like the block or a bracket. If the gauge works then it is the sender's ground.
My thinking is that there is a wire to the gauge going to ground.
True, they did. So do aftermarket suppliers, but the red oxide or gray thread sealer painted onto the threads is a conductive sealer. To test the gauge circuit:
If the gauge shows hot when the engine is cold, disconnect the wires from the sender. If it now hows cold, the wiring is good and the sender is bad.
If the gauge continues to show hot when disconnected, you have a short to ground in the dark green wire.
If it shows cold when the engine is warm, it may be a bad sender. Short the green with tracer wire to ground and if it goes to hot, the circuit is good.
If after replacing the sender it still shows cold, check for an open circuit back to the gauge.
(Condensed from Haynes)
[This message has been edited by fierofool (edited 01-07-2016).]
True, they did. So do aftermarket suppliers, but the red oxide or gray thread sealer painted onto the threads is a conductive sealer.
To test the gauge circuit:
If the gauge shows hot when the engine is cold, disconnect the wires from the sender. If it now hows cold, the wiring is good and the sender is bad.
If the gauge continues to show hot when disconnected, you have a short to ground in the dark green wire.
If it shows cold when the engine is warm, it may be a bad sender. Short the green with tracer wire to ground and if it goes to hot, the circuit is good.
If after replacing the sender it still shows cold, check for an open circuit back to the gauge.
(Condensed from Haynes)
Never rule this out.
Just because its new don't mean its good.
I've seen defective "new" parts many times, especially with these "box store" aftermarket parts.
I corrected my above post. I had been reading the other threads on temperature gauge issues and posted to the wrong thread. Sorry. The circuit check procedures don't apply to the oil pressure sender.
I've seen many a temp gauge sender and oil pressure gauge sender be bad right out of the box. BWD has given me the most problems and Sorensen the next. Even an AC Delco but it turned out to be a repackaged BWD. Echlin or Standard Ignition from NAPA are pricey-er but tend to be more accurate, IMO.
Oil Viscosity? I run 10 w 30 in two of my cars with between 150K and 200k. One's a V6, the other an 88 Duke. The third, with about 15K on new crank kit and cam bearings is running Rotella T 15 w 40.
I corrected my above post. I had been reading the other threads on temperature gauge issues and posted to the wrong thread. Sorry. The circuit check procedures don't apply to the oil pressure sender.
I've seen many a temp gauge sender and oil pressure gauge sender be bad right out of the box. BWD has given me the most problems and Sorensen the next. Even an AC Delco but it turned out to be a repackaged BWD. Echlin or Standard Ignition from NAPA are pricey-er but tend to be more accurate, IMO.
Oil Viscosity? I run 10 w 30 in two of my cars with between 150K and 200k. One's a V6, the other an 88 Duke. The third, with about 15K on new crank kit and cam bearings is running Rotella T 15 w 40.
Testing procedure is basically the same.
I have never seen where oil viscosity had any bearing on a pressure sensor. Ford has (or had?) a oil viscosity sensor if 5w20 wasn't used that would trip the engine light but have no affect on the gauge.
Careful about grounding wires on the oil pressure sender. The orange wire is 12V and is hot at all times. You can blow fuses. The center wire is your ground circuit.
Originally posted by Thunderstruck GT: I have never seen where oil viscosity had any bearing on a pressure sensor.
I'm not sure I understand, if the sensor tells the gauge what the pressure it sees is, higher viscosity will read higher pressure on the gauge.
I was just thinking we need to compare apples to apples, if one guy is running 10w30 his cold oil pressure will be higher than the guy running 5w30, etc. But then I always hear how our Fiero gauges arent real accurate.
But this would be moot to the guy whose gauge reads topped out cold or warm. Unless maybe hes running straight 50 weight
[This message has been edited by 2.5 (edited 01-07-2016).]
I'm not sure I understand, if the sensor tells the gauge what the pressure it sees is, higher viscosity will read higher pressure on the gauge.
I was just thinking we need to compare apples to apples, if one guy is running 10w30 his cold oil pressure will be higher than the guy running 5w30, etc. But then I always hear how our Fiero gauges arent real accurate.
But this would be moot to the guy whose gauge reads topped out cold or warm. Unless maybe hes running straight 50 weight
LOL
Perhaps I should have worded it differently. Yes of course, a higher viscosity will raise the oil pressure a few pounds (mainly cold) but won't raise it enough to cause the OP's issue.
[This message has been edited by Thunderstruck GT (edited 01-07-2016).]
The info below is at least 5 years old and came from Ed Parks of The Fiero Factory:
"A new oil pressure sensor runs $25-50 depending on where you shop. However, be careful what you purchase. There are Taiwanese oil pressure sensors sold as replacements for the V-6 ('85-'88, even though the '88 is different) which are definitely mis-wired internally. They will cause the gauge fuse to blow, the oil pressure gauge to peg, and the fuel pump will not run initially when the ignition is turned to "ON". These sensors come as different brands and in different boxes but all are made in Taiwan. We suggest you try AC Delco sensors and keep the receipt!"
Apparently even AC Delco sensors are suspect. Your best bet may be a junkyard "pull".
Pick up a oil pressure gauge that is mechanical and not electric, electric ones are rarely right, close but they can be off if anything is dirty. A mechanical one will have a mechanical sender that runs oil directly to the gauge. then see what that says.
Not saying that is definitely your problem but I have seen it happen more than once on cars other than Fiero's as well as Fiero's. But by using the mechanical gauge you get a truer reading than most electrical gauge types. Hell when was the last time you changed your oil? it could also be just a clogged sender from to thick an oil.
But to get a real reading try the mechanical oil unit. I keep one in my test box with other test tools like CCC reader, test lights, continuity tester, electrical meter. OLD SCHOOL RULES ! Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Thanks for all your responses.... I was doing some test driving(no plates yet)...not to go to far, then while scanning the guages the oil gauge was working... I was supper excited... When I shut the car off and turned it back on (operating temp) the gauge did not work for a few seconds.... The next day I drove the Fiero a few more times and it seems to work about 98 percent of the time from start up... Could the ignition switch be part of the blame?... The key is pretty worn out which means that the ignition switch could be just as worn, right!
Thanks for all your responses.... I was doing some test driving(no plates yet)...not to go to far, then while scanning the guages the oil gauge was working... I was supper excited... When I shut the car off and turned it back on (operating temp) the gauge did not work for a few seconds.... The next day I drove the Fiero a few more times and it seems to work about 98 percent of the time from start up... Could the ignition switch be part of the blame?... The key is pretty worn out which means that the ignition switch could be just as worn, right!
Thanks again for all your responses Dave
The key being worn out would not affect the gauges, it only turns the other end of the key cylinder, there is a rack if I remember right that the lock cylinder move when the key is turned and that in turn has a rod that goes from there down threw the steering Colum to the actual switch that turns the electrical system on and off. SO I don't think that is your problem. But I would look into getting a new key cut before you get stuck somewhere.
The gauge would have a pause before coming on at operating temps and restarting, fluid is thinner and takes a little longer to get to where the sensor is. a lot of my vehicles have done that, think about when you change the oil and start it for the first time, it takes the gauge a second or 2 to hit the gauge.
Engine is very clean with a fresh LOF service, my brother works at a Chevy stealership... You can eat food off of my engine... Previous owners took really good care of her...because of unknown little things like 02 sensor life and tps life, I'm changing everything just for a piece of mind... She runs very smooth and has plenty of power... Car has 118k but still runs like new.... No rust and a interior that can stand next to a new car... Just a bit of info about my time machine... When and if I have the time, I promise to take lots of pics for you addics out there... Let's see.... The last time I did anything with photobucket was about 10yrs ago, so I have to create a new account or try to remember my UN and PS.
get ~45Ω and ~90Ω resistor. ground and pin B tan wire on plug. (pin A for 88 sender.) 45 is half scale, 90 full scale.
Any other means gauge and/or wiring/ground problems.
old type then upgrade to 88. See my Cave, Oil Sensor
------------------ 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)
