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What is the third fuel line? by Ray_and_kevin
Started on: 03-14-2013 01:56 PM
Replies: 11 (471 views)
Last post by: David Hambleton on 09-15-2013 08:32 PM
Ray_and_kevin
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Report this Post03-14-2013 01:56 PM Click Here to See the Profile for Ray_and_kevinSend a Private Message to Ray_and_kevinEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am in the process of trying to implement a full computer readout for Fieros. I do this stuff for a living and would really like to know what is going on with the ECM while driving. So, I would also like to implement an accurate fuel consumption measurement. There are 3 tubes going into the fuel tank. One is fuel pump out and one is fuel return from the pressure regulator. What is the third hose? I looked in my shop manual and did not see any description of these 3 lines. I am guessing it goes to the fuel canister, but could be way off base.

The hard part at this point is getting fuel metering devices to put in line with the fuel pump and fuel return.
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FieroReinke
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Report this Post03-14-2013 02:00 PM Click Here to See the Profile for FieroReinkeClick Here to Email FieroReinkeSend a Private Message to FieroReinkeEdit/Delete MessageReply w/QuoteDirect Link to This Post
Is it the line that goes to the evap canister?
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Raydar
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Report this Post03-14-2013 04:59 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I believe that's the vapor line that goes to the canister.
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josef644
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Report this Post03-14-2013 06:26 PM Click Here to See the Profile for josef644Click Here to Email josef644Send a Private Message to josef644Edit/Delete MessageReply w/QuoteDirect Link to This Post
87 & 88's had an expansion tank to boot.
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Ray_and_kevin
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Report this Post03-15-2013 03:28 PM Click Here to See the Profile for Ray_and_kevinSend a Private Message to Ray_and_kevinEdit/Delete MessageReply w/QuoteDirect Link to This Post
Thanks Y'all. I missed the trip odometer thread when I posted the original question.

I see that the person doing that product is using the "guess" method of estimating consumption based on injector timing. I am looking at ways of implementing real flow sensors that will measure both inlet flow and fuel tank return. The hard part is getting a good enough seal while still allowing the "gears" to turn.

Also looking at tapping off the fuel gauge line to get an accurate measure of fuel in the tank. I put in a new sending unit and it reads about 2 gallons low. At least I know that when it hits the end, I don't have much range left.

A task for another day when I don't have to fix exhaust bolts and a leaking EGR pipe and a broken windshield washer paddle :-(

Ray
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Marvin McInnis
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Report this Post03-16-2013 09:31 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 josef644:

87 & 88's had an expansion tank to boot.



Correct. On '87/'88 cars the third hose goes to the expansion tank in the right rear wheel well, which is then vented to the fuel evap canister.
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kendallville
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Report this Post03-16-2013 09:49 AM Click Here to See the Profile for kendallvilleSend a Private Message to kendallvilleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Marvin McInnis:


Correct. On '87/'88 cars the third hose goes to the expansion tank in the right rear wheel well, which is then vented to the fuel evap canister.


So that is what that is , I noticed it in the wheelwell last summer when I had the car tore apart. I had no idea what is was or what it was for.
learn something new every day ( I wonder what I forgot to make room )
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82-T/A [At Work]
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Report this Post03-16-2013 10:26 AM Click Here to See the Profile for 82-T/A [At Work]Send a Private Message to 82-T/A [At Work]Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by josef644:

87 & 88's had an expansion tank to boot.



Yeah, what exactly is that for?

Is the expansion tank, the one that sits on the rear passenger side between the engine firewall and the rear quarter panel? If I remember correctly, there's a panel that goes from the tank to that "expansion" tank, and then to the fuel evap canister. But I'm curious exactly how or why this is an expansion tank. Is it for when the fuel expands it'll fill up that tank, or... what exactly does it do?
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1987Fiero_GT
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Report this Post09-15-2013 11:42 AM Click Here to See the Profile for 1987Fiero_GTSend a Private Message to 1987Fiero_GTEdit/Delete MessageReply w/QuoteDirect Link to This Post
I bought a 1987 Fiero GT (V6) and during my two fuel pump replacements, I noticed that the third fuel line coming from the tank had a bolt and hose clamp to block it off.

Is this some sort of modification and if so, is it safe? Will it cause issues? The car runs great with the new FP.

Any input is appreciated.
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Gall757
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Report this Post09-15-2013 12:06 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
The expansion tank was added so there was no possibility of fuel getting sucked into the vacuum canister and messing up the charcoal filter. It's an emissions thing, so depending on how green you are, you can live without it. There may be an increased fuel odor if the evap system is not working.
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Patrick
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Report this Post09-15-2013 02:26 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 1987Fiero_GT:

I bought a 1987 Fiero GT (V6) and during my two fuel pump replacements, I noticed that the third fuel line coming from the tank had a bolt and hose clamp to block it off.

Is this some sort of modification and if so, is it safe? Will it cause issues? The car runs great with the new FP.

Any input is appreciated.


Pontiac obviously added that expansion tank to the '87-'88 Fieros for a reason. (It had to do with the fuel tank also being altered.)

All it should take to repair what you have there is probably just a foot or so of hose.

Do it right, fix it properly!
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David Hambleton
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Report this Post09-15-2013 08:32 PM Click Here to See the Profile for David HambletonClick Here to Email David HambletonSend a Private Message to David HambletonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I read somewhere that the '84 to '86 tanks had an area that would trap air, thereby providing an expansion volume in the event the tank was filled to the cap.

To obtain additional volume for the '87 & '88 tanks, the redesign used the expansion area as well, necessitating a remote expansion tank.

For 82-TA: The expansion tank is on the outside of the unibody (adjacent to the battery), under the plastic outer panel.

[This message has been edited by David Hambleton (edited 09-15-2013).]

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