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Oil sending unit wires. Where do they go? by jimbolaya
Started on: 08-25-2013 05:59 PM
Replies: 40 (692 views)
Last post by: jimbolaya on 09-12-2013 01:49 PM
jimbolaya
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Report this Post08-25-2013 05:59 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
We just got my son's 86 GT started again, after swapping in another engine. The oil gauge is pegged all the way right, and I want to make sure we have the 3 wires on the oil sending unit in the right places before I check other things. There are 3 wires, and I believe one is the one that sends the reading to the gauge, so if it's plugged in to the wrong spot, I assume that might cause a pegging gauge. All 3 wires look the same, and have the same connector. I assume they have different colors, but I haven't peeled back the black plastic cover on them to discover the colors yet. In short, what wire goes where?

Jim
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Report this Post08-25-2013 06:32 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Looking at the top of the sending unit, with the center blade near you, the left one gets the brown wire, the center one gets the white wire and the right one gets the black with tracer. If the connector is unplugged, you will get a pegged gauge, or possibly pointing straight down when the ignition is on.
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Report this Post08-25-2013 07:05 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

Looking at the top of the sending unit, with the center blade near you, the left one gets the brown wire, the center one gets the white wire and the right one gets the black with tracer. If the connector is unplugged, you will get a pegged gauge, or possibly pointing straight down when the ignition is on.


Thank you so much. I'll check that another day. Can't get to it right now. Plus to you.

Jim

[This message has been edited by jimbolaya (edited 08-25-2013).]

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fierofool
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Report this Post08-25-2013 07:33 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Apparently your harness has been cut if you have 3 separate wires. They should go into a molded harness end that will only plug onto the sensor in one direction.
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jimbolaya
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Report this Post08-25-2013 08:37 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

Apparently your harness has been cut if you have 3 separate wires. They should go into a molded harness end that will only plug onto the sensor in one direction.


Possible. The harness came off a bad 86 motor with a rod knock, and some other questionable wiring issues. The donor motor didn't have a wiring harness, so I had to swap the one off the bad motor onto the good motor.

Jim

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jimbolaya
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Report this Post08-29-2013 06:57 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Finally looked at those wires today, and they did not match the colors you gave, but I got it figured out. The wires are orange/black, tan, and tan/white, and that's the order they go on, looking left to right, with the middle tang away from you.

Jim

[This message has been edited by jimbolaya (edited 08-29-2013).]

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Report this Post08-29-2013 07:21 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I took those direct from my 86. I don't know what year the harness is from but it came off the 86 engine that was in the car. Sorry for the bad info.
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Report this Post08-29-2013 09:01 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

I took those direct from my 86. I don't know what year the harness is from but it came off the 86 engine that was in the car. Sorry for the bad info.


No, don't take offense, your information was very helpful, and helped me figure it out. I learned I was missing the plastic cap, and it caused me to dive deeper into the issue. You still have a plus from me, it's all good.

Jim

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Report this Post08-30-2013 07:27 AM Click Here to See the Profile for HudiniClick Here to Email HudiniSend a Private Message to HudiniEdit/Delete MessageReply w/QuoteDirect Link to This Post
You have it figured out but here is a reference in case anyone looks up this thread:



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Report this Post08-30-2013 08:03 AM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Jim, I didn't take offense. I'm just puzzled now as to why my harness has different color wiring. But thanks, Hudini. Now maybe I can trace down why my gauge pegs.
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Report this Post08-30-2013 03:02 PM Click Here to See the Profile for commodore_dudeSend a Private Message to commodore_dudeEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

Jim, I didn't take offense. I'm just puzzled now as to why my harness has different color wiring. But thanks, Hudini. Now maybe I can trace down why my gauge pegs.


Have you tried replacing the sender? Mine was pegging when I bought it and a new sender sorted it out (bit different being an 88, but the pre-88 sender is even more likely to fail right?)
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Report this Post08-31-2013 06:46 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Hudini:

You have it figured out but here is a reference in case anyone looks up this thread:




Thanks for the chart Hudini. I'd give you a plus, but you already have one from when I first joined the forum. you were one of the first guys to ever help me out.

Jim

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Report this Post09-05-2013 07:16 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well finally got a permanent battery. After hooking up the wires and starting the car, the gauge still pegs far right. I then unplugged the sending unit, and the gauge remained pegged to the right. How can I test the sending unit? Can I ground one of the connections and determine if it works or not? Gonna try search in the mean time.

Jim
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Report this Post09-05-2013 08:00 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
According to what little I found through search, the needle will peg to the right if it's unplugged. Well it does that even when it's plugged. Is that telling me the sending unit is bad? I called Advance and a new unit is only $15. Probably worth throwing a new part at it whether it's needed or not.

Jim
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Report this Post09-05-2013 08:46 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just went through what you are doing. Mine was a 3100 swap, but same thing. One wire goes to the gauge and light, if it is open the gauge pegs, if you short it to ground the gauge goes to zero and the light comes on. The other two are the fuel pump on off switch. When the fuel pressure hits about 3 PSI they close to each other and the fuel pump relay pulls in and the pump will run. With the key on short the two outside wires together and the fuel pump should run. If you ground the center wire then the needle should go to zero and the light should come on. The $15.00 pressure sensor is likely the wrong one, it does have the pump contacts but only an on and off for the pressure, you need one with the pressure sensor, if the sender is not about 2 inches + long it is the wrong one. Larry

[This message has been edited by trotterlg (edited 09-05-2013).]

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Report this Post09-05-2013 09:10 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

Just went through what you are doing. Mine was a 3100 swap, but same thing. One wire goes to the gauge and light, if it is open the gauge pegs, if you short it to ground the gauge goes to zero and the light comes on. The other two are the fuel pump on off switch. When the fuel pressure hits about 3 PSI they close to each other and the fuel pump relay pulls in and the pump will run. With the key on short the two outside wires together and the fuel pump should run. If you ground the center wire then the needle should go to zero and the light should come on. The $15.00 pressure sensor is likely the wrong one, it does have the pump contacts but only an on and off for the pressure, you need one with the pressure sensor, if the sender is not about 2 inches + long it is the wrong one. Larry



Thanks I'll give this a try in the morning, but to be clear, if I ground the middle peg, it will go to zero if it's working properly, or if it's broken? And what light are you talking about, the check engine light?

Jim
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Report this Post09-05-2013 09:22 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you gound the wire that goes to the middle connection the gauge should go to zero and (on my 86 GT) the red light for the oil pressure comes on. Larry
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Report this Post09-06-2013 08:38 AM Click Here to See the Profile for racingforthesonSend a Private Message to racingforthesonEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Hudini:

You have it figured out but here is a reference in case anyone looks up this thread:




So from this it looks like if the Oil Sending Unit reads low then it would kill the fuel pump?
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Report this Post09-06-2013 09:25 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

If you gound the wire that goes to the middle connection the gauge should go to zero and (on my 86 GT) the red light for the oil pressure comes on. Larry


OK, so I did this, and the needle went to zero. However, I still need interpretation of the data. Is the oil sending unit good or bad?

Jim

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Report this Post09-06-2013 10:33 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

....The $15.00 pressure sensor is likely the wrong one...


You were right on this. Oil sending unit is $56. $15 would have been nice.

Jim

[This message has been edited by jimbolaya (edited 09-06-2013).]

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Report this Post09-06-2013 10:45 AM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jimbolaya:


You were right on this. Oil sending unit is $56. $15 would have been nice.

Jim



Yep...there ya go. My gauge is doing the same....and that $56 is the reason that I haven't gotten around to fixing it yet

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Report this Post09-06-2013 11:48 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is one made that is listed for an 88 fiero which is about $25.00, I bought that one and it works perfect, only difference is that it uses a smaller connector than the big unit. I will post some part numbers later today. Larry
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Report this Post09-06-2013 11:52 AM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post

trotterlg

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OK, these three will work, only difference is the connector on top. Oil pressure sender
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jimbolaya
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Report this Post09-06-2013 12:05 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the part recommendation. It has me thinking though. The engine is an 88, I swapped it into my sons 86. I'm pretty sure that the oil sending is the one that was on the 88 engine. So could that be part of my problem? An 88 oil sending unit with a 86 computer and car?

Jim
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Report this Post09-06-2013 12:23 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jimbolaya:

Thanks for the part recommendation. It has me thinking though. The engine is an 88, I swapped it into my sons 86. I'm pretty sure that the oil sending is the one that was on the 88 engine. So could that be part of my problem? An 88 oil sending unit with a 86 computer and car?

Jim


As I understand it, you can use the 88 sender in an 86 car. The only thing you need to do is get the right connector for the 88 sender (they are different) and get it spliced in right. Ogre has the details in his cave. I don't believe the computer is an issue as long as you have the sender wired in correctly

[This message has been edited by 92wastheyear (edited 09-06-2013).]

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Report this Post09-06-2013 12:36 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
All three are electrically identical function, only difference is the physical size and the connector on top. Larry
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Report this Post09-07-2013 06:08 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jimbolaya:


OK, so I did this, and the needle went to zero. However, I still need interpretation of the data. Is the oil sending unit good or bad?

Jim


I'm gonna ask one more time, because this question really hasn't been answered. I grounded the middle wire, and the needle went to zero, and the light came on. Does this mean the sender is bad, or does it mean it's ok?

Jim

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Report this Post09-07-2013 06:21 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
If you ground the middle wire and the gauge goes to zero and the light comes on and with it plugged into the sendsor/sender the gauge stays pegged no matter if the car is running or not then the sender is bad. Larry
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Report this Post09-07-2013 09:37 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

If you ground the middle wire and the gauge goes to zero and the light comes on and with it plugged into the sendsor/sender the gauge stays pegged no matter if the car is running or not then the sender is bad. Larry


Thank you. It is bad then. Didn't want to spend $56 for a new one, but that is better than having to take the engine out again to find out what might be wrong.

Jim

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Report this Post09-07-2013 09:50 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
Don't spend $56.00 spend $22.00 on the one for an 88 and swap the connector. Larry

[This message has been edited by trotterlg (edited 09-07-2013).]

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Report this Post09-07-2013 09:59 PM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by trotterlg:

Don't spend $56.00 spend $22.00 on the one for an 88 and swap the connector. Larry





The connector is around $20 too...so it is still a better deal....and a better sender

[This message has been edited by 92wastheyear (edited 09-07-2013).]

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Report this Post09-07-2013 10:18 PM Click Here to See the Profile for trotterlgClick Here to Email trotterlgSend a Private Message to trotterlgEdit/Delete MessageReply w/QuoteDirect Link to This Post
I bought this one, about $11.00 delivered. Connector
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jimbolaya
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Report this Post09-08-2013 07:47 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks for the suggestions guys. I think I'll go that route.

Jim
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Report this Post09-08-2013 08:38 AM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Jim, what I do is to remove the electric sender and screw in a mechanical gauge in its place. Start the car and check the oil pressure against a mechanical gauge. Then you have something to compare the information from the electric sender. You can pick up a mechanical gauge for under $20 and it will help you many times while you own a Fiero. Due to the poor quality of the BWD senders and some of the others that seem to all be made by the same foreign manufacturer, I never trust the reading of a new sender until I've compared it to the reading of a mechanical gauge.

In reading your question about grounding the center wire, if I understand you correctly, you are only testing the gauge circuit since the sender must be uplugged to access the center lead of the harness. That test can tell you if your gauge is calibrated correctly, but won't tell you if the sender is working correctly.

If the sender is removed and plugged into the harness, you can ground the threaded base against the ground wire on the deck lid hinge. You should get a reading of zero if the sender is accurate at the low end. It doesn't mean it's accurate at the higher pressure ranges. This can be done with a new sender before installation. That reading should agree with the reading you get by simply grounding the center lead.

I have been searching for some time for a fitting that would allow me to install a mechanical gauge alongside the stock electric gauge. I found one at Grainger. It has one 1/4NPT male and two female 1/4 NPT fittings. It's Grainger item 4VPV7, listed as Eaton 2092-4-4S if anyone is interested.
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Report this Post09-09-2013 09:27 AM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by racingfortheson:

So from this it looks like if the Oil Sending Unit reads low then it would kill the fuel pump?



No. It provides an alternate means of powering the fuel pump when there is oil pressure. It is in parallel with the ECM-driven fuel pump relay.


 
quote
Originally posted by jimbolaya:

So could that be part of my problem? An 88 oil sending unit with a 86 computer and car?



No. All Fiero OP senders are mechanically and electrically compatible. Only the connectors are different.


 
quote
Originally posted by jimbolaya:

I'm gonna ask one more time, because this question really hasn't been answered. I grounded the middle wire, and the needle went to zero, and the light came on. Does this mean the sender is bad, or does it mean it's ok?



Neither. It means that the gauge and the wiring to it are working correctly. That implies, but doesn't guarantee, that the OP sender may be bad. Another possibility is that the OP sender may not be grounded properly ... e.g. if PTFE tape was used on the threads.

Troubleshooting is often a process of determining what isn't bad, eventually narrowing the problem to a single possible cause.
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Report this Post09-09-2013 10:30 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Marvin McInnis:


Another possibility is that the OP sender may not be grounded properly ... e.g. if PTFE tape was used on the threads.



Hey Marvin, I saw this in another thread you mentioned it in. You recommended some type of thread sealant or some such thing. Now I can't find the thread. Can you mention what you recommend again in this thread?

Jim

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Report this Post09-09-2013 10:41 AM Click Here to See the Profile for 92wastheyearClick Here to Email 92wastheyearSend a Private Message to 92wastheyearEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jimbolaya:


Hey Marvin, I saw this in another thread you mentioned it in. You recommended some type of thread sealant or some such thing. Now I can't find the thread. Can you mention what you recommend again in this thread?

Jim


I believe this actually come out of the box with some proper sealant already on the threads. You should be able to just screw it right in

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Report this Post09-09-2013 10:56 AM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 92wastheyear:


I believe this actually come out of the box with some proper sealant already on the threads. You should be able to just screw it right in


Good to know. I have an 88 Sending unit, and pigtail on order now, and it was $10 cheaper than the 84-87 unit.

Jim

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Report this Post09-09-2013 12:19 PM Click Here to See the Profile for Marvin McInnisClick Here to visit Marvin McInnis's HomePageSend a Private Message to Marvin McInnisEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by jimbolaya:

You recommended some type of thread sealant ... Can you mention what you recommend again in this thread?



Any liquid or paste-type thread sealant rated for use with oil should work fine. You don't need much. As 92wastheyear said, your new OP sender may have a dab of sealant already applied to the threads, in which case you probably don't need to use anything else. Just don't use a tape-type thread sealant.

[This message has been edited by Marvin McInnis (edited 09-09-2013).]

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jimbolaya
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Report this Post09-11-2013 02:25 PM Click Here to See the Profile for jimbolayaClick Here to Email jimbolayaSend a Private Message to jimbolayaEdit/Delete MessageReply w/QuoteDirect Link to This Post
You can always count on Advance to put you behind a week or two. Stupid Oil pressure sending unit had the wrong thread size. I had to go back and exchange for the right one. Which means I wait another day for the part.

Jim
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