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How to get the fuel sender level to be seen by the obdII by Tweeder
Started on: 05-27-2014 06:51 PM
Replies: 19 (1448 views)
Last post by: Tweeder on 05-29-2014 11:11 AM
Tweeder
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Report this Post05-27-2014 06:51 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have the ultra guage and in it for calculating the dte it would normally use the fuel sensor level but my vehicle doesn't support that in the obdII it says. So how do I get it to recognize it or do I have to wire it to certain pins in. The PCM? I see in the wiring swap diagram, it shows blue pin 3 is "fuel level output control circuit", connector clear pin 69 says " fuel level sensor input" and those get deleted.

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[This message has been edited by Tweeder (edited 05-27-2014).]

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hookdonspeed
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Report this Post05-27-2014 08:41 PM Click Here to See the Profile for hookdonspeedClick Here to visit hookdonspeed's HomePageClick Here to Email hookdonspeedSend a Private Message to hookdonspeedEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Tweeder:

I have the ultra guage and in it for calculating the dte it would normally use the fuel sensor level but my vehicle doesn't support that in the obdII it says. So how do I get it to recognize it or do I have to wire it to certain pins in. The PCM? I see in the wiring swap diagram, it shows blue pin 3 is "fuel level output control circuit", connector clear pin 69 says " fuel level sensor input" and those get deleted.


clear pin 69 would need to be wired into the sensor line from the 3pin fuel pump connector on the firewall. not sure if the signal is compatible tho, should be, but the values are obviously going to be different as the tank size is not the same.
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Tweeder
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Report this Post05-27-2014 08:53 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by hookdonspeed:


clear pin 69 would need to be wired into the sensor line from the 3pin fuel pump connector on the firewall. not sure if the signal is compatible tho, should be, but the values are obviously going to be different as the tank size is not the same.


Can someone confirm what wire that I will need to splice and bring to clear pin 69? I'll ave to look but I think I can play with the tank size with hptuners

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phonedawgz
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Report this Post05-27-2014 09:16 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
The fuel level input needs to be from a 0 - 5v sender, not the stock Fiero one.

The fuel gauge output will then run to your dash. I am not sure if it will work with the Fiero dash gauge however.
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Report this Post05-27-2014 09:45 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

The fuel level input needs to be from a 0 - 5v sender, not the stock Fiero one.

The fuel gauge output will then run to your dash. I am not sure if it will work with the Fiero dash gauge however.


So I would need a fuel setup from a Grand Prix then? Or just the sending unit. Why would I need to run it to the dash if there's one already there, wouldn't I run it to the pin 69 that way the PCM will see the level and pass the info through the obdII and into my guage.

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[This message has been edited by Tweeder (edited 05-27-2014).]

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phonedawgz
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Report this Post05-27-2014 11:10 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
With more complex evaporation control systems, the PCM needs to know the fuel level to run the tests correctly. To do this, rather than have two senders in the tank, one for the PCM and one for the gauge, GM designed the dash gauge to run off of the PCM output. GM couldn't run the PCM by tapping onto the existing gauge sender since the the voltage received would vary depending on the internal resistance of the dash gas gauge itself, and because the wiring of the gas gauge will allow the voltage on the gas gauge wire to go up to vehicle voltage. PCM inputs need to be between 0 and 5v. Thus GM designed a potentiometer type sender for the fuel level. Then to keep the dash gauge going there the PCM had to have a gauge output signal.

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Report this Post05-27-2014 11:36 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

With more complex evaporation control systems, the PCM needs to know the fuel level to run the tests correctly. To do this, rather than have two senders in the tank, one for the PCM and one for the gauge, GM designed the dash gauge to run off of the PCM output. GM couldn't run the PCM by tapping onto the existing gauge sender since the the voltage received would vary depending on the internal resistance of the dash gas gauge itself, and because the wiring of the gas gauge will allow the voltage on the gas gauge wire to go up to vehicle voltage. PCM inputs need to be between 0 and 5v. Thus GM designed a potentiometer type sender for the fuel level. Then to keep the dash gauge going there the PCM had to have a gauge output signal.


It looks in hptuners, i can play with the tank size. http://www.ls1gto.com/forum...wthread.php?t=399573
So with that, could I run a wire from the fiero sender (not sure which wire)or guage cluster to pin 69 and that will tell the PCM what the level is at and then calibrate the tank size through that? Or is the voltage thingy going to be my problem?
Also my guage is not correct right now it looks like it's about 1/8-1/4 tank off as I recently ran out of fuel while in my garage tuning.
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[This message has been edited by Tweeder (edited 05-27-2014).]

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phonedawgz
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Report this Post05-27-2014 11:52 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
No you can't use the Fiero sender.

FYI also - while it looks like the other senders will just drop into the hole on the Fiero tank, the newer senders have a bigger hole in the tank.

[This message has been edited by phonedawgz (edited 05-27-2014).]

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Report this Post05-27-2014 11:55 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

No you can't use the Fiero sender.


So what's the easy way around this? I do have a spare potentiometer from the tach swap if that helps.

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phonedawgz
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Report this Post05-27-2014 11:59 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
You will have to figure out how to get a potentiometer type sending unit into the tank.
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Report this Post05-28-2014 12:14 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

You will have to figure out how to get a potentiometer type sending unit into the tank.


I thought that sending units are potentiometer as they vary the voltage depending on where the float is. Going back to your earlier comment " The fuel level input needs to be from a 0 - 5v sender, not the stock Fiero one. The fuel gauge output will then run to your dash. I am not sure if it will work with the Fiero dash gauge however." How is the fiero sending unit calculated?

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Report this Post05-28-2014 01:57 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post

Tweeder

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I was just looking over that link I posted earlier and was thinking since I can change the fuel sender ohms, why can't I put them to match the fiero values? Then it would tell the PCM the same levels the fiero guage is showing thus giving me a proper distance to empty. If that is so, what wires do I need from where to where? I'm thinking I only need one, pin 69 coming from the fuel guage sending wire( which would be?).

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Report this Post05-28-2014 05:06 AM Click Here to See the Profile for PaulJKSend a Private Message to PaulJKEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Tweeder:

... what wires do I need from where to where? I'm thinking I only need one, pin 69 coming from the fuel guage sending wire( which would be?).



The bottom line is that it is not possible to do by running wires.

Think of it like this: The fiero sender was not designed to output the signal you're trying to get (it's OBD-1). You need to change the sender completely (and modify the tank because there are no alternatives that are plug-n-play) or redesign the fiero sender then fabricate the changes to the fiero sender (i also have a 3800SC car and would like to have the OBD-2 fuel output).


 
quote
Originally posted by Tweeder:

So what's the easy way around this?



There isn't one.

Hope this helps.

[This message has been edited by PaulJK (edited 05-28-2014).]

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phonedawgz
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Report this Post05-28-2014 07:47 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Crap

I made a mistake. I was thinking it was the fuel level sender but instead it was the fuel tank pressure sender that is the potentiometer. The OBD2 sender is just a variable resistor. I do not know what the resistive range of the sender is.

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Report this Post05-28-2014 01:36 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

Crap

I made a mistake. I was thinking it was the fuel level sender but instead it was the fuel tank pressure sender that is the potentiometer. The OBD2 sender is just a variable resistor. I do not know what the resistive range of the sender is.



I read that the fender values are 0-90 ohms

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Tweeder
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Report this Post05-28-2014 01:40 PM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post

Tweeder

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quote
Originally posted by PaulJK:


There isn't one.

Hope this helps.



I'm not arguing just chewing on this. I realize the sender values are obdI and the swapped PCM wants obdII, but aren't ohms, ohms regardless of obd? If that's the case then it should be as simple as putting in the fiero values..... As I can change tank size and sender readings in hptuners ad per the gto link. Please correct my way of thinking as I am wrong more that right, lol

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PaulJK
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Report this Post05-28-2014 11:31 PM Click Here to See the Profile for PaulJKSend a Private Message to PaulJKEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, if you just need ohms you should be able to tap into the wire going into the fuel guage from the sender. There are only 3 wires from the fuel tank; power (for the fuel pump, ohms out to the fuel level guage, and ground. The pink wire from the sender at C3, 7 plugging into the instrument cluster.





I guess you can try it and tell us all if it works .

The (other) problem i see is that the fiero sender is notoriously inaccurate. The sender itself is a poorly designed piece of junk that wiggles in every direction as it wears. I've stopped rebuilding them because the quality is so bad. I rebuilt my own and ran out of gas when my digital guage read 40%. Other times it's just fine. You can read through the archives and find the same problem many many times (Almost Everybody uses mileage as an indicator of fuel remaining, not the gas guage). So i'm saying that even if you get the output you need, it still might not be worth much.

First I'd try tapping into the guage wire and see if the signal is compatible. If it works, I'd rebuild the sender using a VDO sender board or something else that will give reliable, consistent 0-90 ohm readings. Here's how one PFF did it using the VDO sender:

http://www.fiero.nl/forum/A...090219-2-078597.html

Good luck. Hope it works for you Keep us informed.

[This message has been edited by PaulJK (edited 05-29-2014).]

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Tweeder
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Report this Post05-29-2014 01:28 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
Crap, after all that I just found out that they don't have that option set up for my vehicle, and I,m not sure if and when it will be available.

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PaulJK
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Report this Post05-29-2014 03:13 AM Click Here to See the Profile for PaulJKSend a Private Message to PaulJKEdit/Delete MessageReply w/QuoteDirect Link to This Post
Well, i think there may be a way to get what you want (assuming that the input was ohms as previously discussed).

Feed the ohms reading into the PCM by running the correct wiring ;
Turn ON the input in the PCM software so the PCM accepts the ohms input;
Use an Android tablet and the Torque Pro ($4.95) or similar software (it is not vehicle specific and will allow you to set PIDs or sensor inputs).

That's what i would do if your ohm thing works. I've been using Torque Pro on my android tablet in my car and it's pretty good (not perfect) software.

https://play.google.com/sto...?id=org.prowl.torque

OK. now you owe me a +

[This message has been edited by PaulJK (edited 05-29-2014).]

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Report this Post05-29-2014 11:11 AM Click Here to See the Profile for TweederSend a Private Message to TweederEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by PaulJK:

Well, i think there may be a way to get what you want (assuming that the input was ohms as previously discussed).

Feed the ohms reading into the PCM by running the correct wiring ;
Turn ON the input in the PCM software so the PCM accepts the ohms input;
Use an Android tablet and the Torque Pro ($4.95) or similar software (it is not vehicle specific and will allow you to set PIDs or sensor inputs).

That's what i would do if your ohm thing works. I've been using Torque Pro on my android tablet in my car and it's pretty good (not perfect) software.

https://play.google.com/sto...?id=org.prowl.torque

OK. now you owe me a +



You sir have a +. I'll look into turning on the input in the PCM, I believe it would already be enabled as that feature would have been used in the original car"..I hope for simplicity sakes. Unfortunately I do not own an android but multiple apples. I am using dashcommand and will look into that to see if it can be done. Thanks for your info.

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