I'm converting my 1986 oil pressure sender to the later 1988 style, and I'm reading conflicting info when it comes to wiring up the new style connector...
They are both 3 wire, and some posts in the archives say the middle wire is the ground, while the other two are interchangeable.
So I'm looking for clarity on this...
1. When they say the center wire is ground, I assume they are talking about the 1986 connector with tan wire? 2. When I look at the NEW 1988 sender socket pins, the pin on the LEFT is marked "G", doesn't that indicate ground?
I've read people doing conversion and new 1988 style doesn't last long, shorting out, or fuel pump continues to run after ignition off...
Would like to get some feedback on this from somebody who has been there is knows for sure, thanks.
[This message has been edited by Skybax (edited 06-07-2021).]
I'll be following this with interest - what are the benefits of this exchange?
The benefits are replacing an early low reliability unit.a later high reliability sensor. ------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
[This message has been edited by Dennis LaGrua (edited 06-09-2021).]
I converted my 87 to an 88 style more than 2 years ago. Still works. I went a step further and mounted my sender right off the block using an adapter and 45 degree elbow. I also used Ogres site for the wiring.
I've read people doing conversion and new 1988 style doesn't last long, shorting out, or fuel pump continues to run after ignition off...
Would like to get some feedback on this from somebody who has been there is knows for sure, thanks.
There was a run of mis-wired 88-style oil pressure switches a few (more than ten) years back. I would suspect that they have all worked their way through the system, by now. (There was no question. Plugging them in usually caused the fuse to blow, IIRC.)
About 5 years ago, I also installed one that seemed to stick, and kept the fuel pump turned on, even with the key/engine off. I got tired of such silliness, and switched my fuel pump to a switched circuit. Some people would say that this is ill-advised, but it has caused me exactly zero issues. But then I'm not running a high capacity pump, either.
[This message has been edited by Raydar (edited 06-09-2021).]
I haven't had any problem with the conversion on my 86 that was done 7 years ago in the link Raydar posted. (Thanks, Steve) That can't be said of my 87 which I converted maybe 2 years ago.
The first unit began blowing my instrument panel fuse so that no gauges other than the speedometer would work. I returned it for a replacement and that one worked for a while then began doing the same. So, I just unplugged it and left the oil pressure gauge pegged full right bottom.
I had a used one (don't remember where I got it) and eventually installed it. It worked for a while, then the fuel pump wouldn't shut off and it blows the gauge fuse. So again, the sending unit is unplugged and the gauge is pegged far right bottom. I've verified that it's wired correctly, so that isn't the problem.
I don't remember what brands I had, but I got all of them from Rock Auto, except the used one. If you do the conversion, get a good name-brand sending unit.
I switched to the '88 style oil pressure sender, because the early type would only last 6-12 months before they started leaking oil. That got pretty annoying. I was able to get the pigtail from an '88 Fiero wiring harness. The wire colors were the same. So I just connected the same color wires together.
At the time I did my 86 as shown in my thread, I didn't want to work outside for a period of time trying to splice and solder the wires, so I made the temporary connections. It's actually still working well at this time. When I did my 87, it was more suitable weather and the new terminal was hardwired in with solder and heat shrink tubing. With the fuses blowing, I questioned my work and went back to verify correct wiring.
Prior to making my trip to Carlisle GM Nationals Fiero Show and then all the way to Millinocket, Me. at the end of this month, I have ordered a replacement ACDelco sending unit to see how it holds up.
Installed my Made in Mexico Delco sender this afternoon, used butt connectors with heat shrink, back filled the new connector with dielectric grease, covered the wires and top of new sender with GM split wire loom. Everything looks good and no more dancing needle, hopefully I don't experience any of the weirdness mentioned above.
Have to admit I was a little hesitant to do this mod to my mostly stock car, especially with hearing history of problems above, but ultimately decided to go forward with it because it seemed the better of the only 2 options. I didn't want to install a new aftermarket old-style sender due to poor connector and prone to leaking. Have to give my original sender credit, it lasted 36 years and still doesn't leak, it was the dancing needle and crappy connector that I was tired of.
[This message has been edited by Skybax (edited 06-09-2021).]
There was a run of mis-wired 88-style oil pressure switches a few (more than ten) years back. I would suspect that they have all worked their way through the system, by now. (There was no question. Plugging them in usually caused the fuse to blow, IIRC.)
About 5 years ago, I also installed one that seemed to stick, and kept the fuel pump turned on, even with the key/engine off. I got tired of such silliness, and switched my fuel pump to a switched circuit. Some people would say that this is ill-advised, but it has caused me exactly zero issues. But then I'm not running a high capacity pump, either.
I remember 15 years ago Ed Parks from The Fiero Factory mentioned this, but I recall it was for 85-87V6 oil pressure senders. Not 88. If so, do you remember what brand?
We took the Fiero to first cruise/show yesterday and halfway there I discovered I had no dash lights.
(Side Note A: Yes it is wired correctly according to info provided on Orge's site and in forum archives) (Side Note B: This car is in excellent original condition throughout and dash lights worked prior to this mod)
Here are the preliminary diagnostic findings...
1. No dash lights at all (including aux pod) 2. Radio clock is brightly illuminated with parking/dash lights off (normal) 3. Radio clock is completely out with parking/dash lights turned on (not normal, should be half illuminated) 4. Everything else works 5. All fuses are good 6. With everything off I have power to both sides of these fuses (#11 horn/int lights, #3 parking lights, #2 oil psi sender/fuel pump) 7. If I disconnect NEG side of batt and put test light between NEG batt and NEG batt terminal, I get dim light that fades out within 5 sec 8. Pulling one fuse at a time, if I disconnect NEG side of batt and put test light between NEG batt and NEG batt terminal, I still get dim light that fades out within 5 sec 9. Doesn't matter if the 1988 style oil sender is connected or not, all diagnostics give same results
I was hesitant in doing this mod and should have left it alone. My instinct tells me it wasn't defective switches 10 years ago, but maybe an incompatibility with this mod that causes collateral damage and yet to be discovered based on others having similar symptoms/malfunctions.
Disclaimer: I don't want to sound like a whiny "woe as me" victim but what really sucks about this is, I busted my butt on this car non-stop for the last 6 weeks (about 200 hours) in addition to my normal job to get it ready so the wife and I could enjoy some shows with friends this summer. Long story short, got into Fiero's about 20 years ago when wife and I first moved in together and we had lots of good times those years, then got into other cars/biking. Fast forward to 2013 where I had 4 separate major traumas in a 9 month period that totaled me. Most people don't come back from that, trust me I know, because western medicine is very limited and had me down the wrong path. It took me 5 freaking years and 5000 hours of study to find the truth and recover, and I did it without any meds or alcohol, so the only reason I'm able to type this message and do these things with a 99% recovery is because of God and my Wife combined with raw courage/faith/determination. So the whole point of buying a Fiero this Spring was so the wife and I could reminisce 2000-2005 and celebrate our victory on backside of 2020 nonsense. This was our first weekend out and wasn't able to go to the big car event today because I'm not comfortable taking it on a road trip with electrical malfunction due to this mod.
I'm deflated right now and don't know where to start, any help from electrical guru's would be appreciated...
[This message has been edited by Skybax (edited 06-13-2021).]
The oil pressure sensor is not part of the illumination circuit. So it can't affect the dash lights. The issue with the dash lights is just coincidental.
The dash lights run off the INST fuse. I know you said the fuses are all good, but check that one again.
As a previous auto tech many years ago I agree that "coincidental stuff" can lead you down the wrong path pulling your hair out, however for others to have similar coincidental issues is often not coincidental, even when it shouldn't/doesn't make sense on paper (same as other things in life).
Can you please tell me if power to both sides of fuse #2 (oil psi sender/fuel pump) with key off is normal or not normal so I can rule out normal operation?
Also, why is there a low volt test light that fades out within 5 seconds doing a parasitic draw test? And why does it come back / can be repeated over and over if you wait 15 seconds to retest? It acts like residual bleed of small amount of energy, shouldn't normal be no light at all?
[This message has been edited by Skybax (edited 06-13-2021).]
OK, now we're getting somewhere. Sounds like the dimmer transistor is bad.
The dimmer switch doesn't directly control the lights. It sends a signal to a transistor. The transistor uses that signal to determine how much power to send to the dash lights. That green wire you mentioned (should be dark green with white stripe) goes to the dimmer transistor. Also, the transistor powers the INST fuse.
So if you have power going through the dimmer switch, but the INST fuse has no power, then something's up with the transistor. That transistor is mounted under the dash, beside the steering column. It has an aluminum heatsink. See photo in link below.
There should be 3 wires attached to the transistor. The brown wire is power from the headlight switch. The dark green with white stripe is signal from the dimmer switch. The dark green wire is power to the dash lights. You can test the circuit by jumping the brown wire to the green wire. That will bypass the transistor and send power to the dash lights (if the parking lights are on). If the dash lights come on when you bypass the transistor, then the transistor is dead. You can buy the one in the link above for a reasonable price.
I installed my new ACDelco sending unit. Doesn't blow the fuse any more. Gauge still stays pegged to the far right bottom as if it doesn't have a ground.
Does anyone have a known good used sending unit they're willing to sell?
[This message has been edited by fierofool (edited 06-13-2021).]
------------------ 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)
OK, now we're getting somewhere. Sounds like the dimmer transistor is bad.
The dimmer switch doesn't directly control the lights. It sends a signal to a transistor. The transistor uses that signal to determine how much power to send to the dash lights. That green wire you mentioned (should be dark green with white stripe) goes to the dimmer transistor. Also, the transistor powers the INST fuse.
So if you have power going through the dimmer switch, but the INST fuse has no power, then something's up with the transistor. That transistor is mounted under the dash, beside the steering column. It has an aluminum heatsink. See photo in link below.
There should be 3 wires attached to the transistor. The brown wire is power from the headlight switch. The dark green with white stripe is signal from the dimmer switch. The dark green wire is power to the dash lights. You can test the circuit by jumping the brown wire to the green wire. That will bypass the transistor and send power to the dash lights (if the parking lights are on). If the dash lights come on when you bypass the transistor, then the transistor is dead. You can buy the one in the link above for a reasonable price.
Best of luck!
Update... 5 minutes after you posted your message yesterday a storm cell came thru with micro-burst and knocked out power for the last 20+ hours, so the power just came back on about 30 minutes ago. Yes you are correct, when I disconnected the connector for the transistor and jumped dark brown to green the dash lights lit up, so I'm going to buy one from Rodney. Thank you for assisting me in helping to figure out a frustrating problem within 24 hours, because it might have taken me all week to figure out without your help, and just in time before the storm hit, thanks again!
[This message has been edited by Skybax (edited 06-14-2021).]
I installed my new ACDelco sending unit. Doesn't blow the fuse any more. Gauge still stays pegged to the far right bottom as if it doesn't have a ground.
Does anyone have a known good used sending unit they're willing to sell?
I purchased an NOS 85-87 oil pressure sender and going to make my own connector because I'm going back to the original style. So if you want to buy my new 1988 AC Delco oil sender that was installed on my car for only a few days you can have it (and the new connector) for half price shipped.
(gauge worked perfectly and had no issues, aside from the coincidental dash light dimmer transistor failure).
I'm currently swamped with tasks due to no power last 24 hours so just send me PM if you want it...
[This message has been edited by Skybax (edited 06-14-2021).]
Originally posted by Skybax: Thank you for assisting me in helping to figure out a frustrating problem within 24 hours, because it might have taken me all week to figure out without your help, and just in time before the storm hit, thanks again!
Well, I picked up Skybax's known good 88 sending unit and installed it today. As described above, the ACDelco unit I was running was keeping the gauge pegged and I discovered that the fuel pump was also continuing to run. The first 88 sender was a Standard Ignition part and it would blow the fuse for the instrument panel as soon as I turned on the ignition.
Surprise! The ACDelco unit from Skybax blows the fuse, also. So, I have a Standard Ignition and an ACDelco sender that both blow the fuse and another ACDelco sender that keeps the gauge pegged and the fuel pump energized. It has me puzzled as to whether it's sending units or wiring. If it's wiring, I shouldn't get 2 different problems, especially with the same brand units. I put my old ACDelco back in after replacing the fuse, and it pegs the gauge with with ignition on and keeps the fuel pump energized with ignition off. So, it's currently unplugged, just leaving the gauge pegged.
Time to re-recheck the harness conversion and maybe replace the gauge unit. I would also welcome any ideas. Anyone know how to test the sending unit with it out of the car?
BTW, to skybax. When he learned that the unit didn't solve my problem, he refunded half the already discounted price I paid him for his new ACDelco sender.
[This message has been edited by fierofool (edited 06-21-2021).]
My instinct tells me it has nothing to do with oil gauge aspect, because that doesn't come into play yet when you turn the ignition on, so the fuel pump circuit does go live when you turn the key on via the ecm which energizes fuel pump for a few seconds, and the #2 oil sender / fuel pump fuse is hot through the fuse box at all times.
With the oil sender disconnected, does it still prime the pump the same and start up relativity quickly?
Does the car stay running if you unplug the oil sender while running?
I will meditate on this some more...
[This message has been edited by Skybax (edited 06-21-2021).]
It has always taken 2 or 3 attempts to start when it's cold. It starts quickly when warmed. New fp relay. The pump primes with or without the sender plugged up. Gauge stays pegged with or without the sender plugged up, except for the ones that blow fuses. I've been running it for months with the sender unplugged. I'm still running the original fuel pump.
The cold start injector was working. I upgraded the injectors a few months back and was getting a very rich burn. I thought the cold start had an issue so I disconnected it. I eventually had to go back to my original injectors, but I just left the cold start injector disconnected. It takes 2 or 3 primes with or without the injector connected. I think it may just be a 34 year old fuel pump causing the long starts.
