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2G GSX fuel tank question

Posted by techboy, Sep 16, 2020

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  1. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    About a 1 1/2 years ago I swapped my GST to GSX. What did you guys do with this vapor line the runs from the fuel cut off valve? (see pic below). My car is a 99, so the 99 GST tank had a TON of evap crap on it when I pulled it. The GSX tank I swapped on was off a 97 and much simpler, but I'm trying to remember what I did with this line during the swap ... I feel like I connected it to something.

    LfLFrO.jpg

    Reason I'm asking is I've been a problem with my car stalling out while driving shortly after filling up. I think it's got something to do with fuel tank pressure. I noticed today when I unscrewed the fuel cap it seemed to release a lot of pressure - more than when it was a GST. Do you just let it hang? install a check value on the end? or does is it get connected somewhere during the swap? I need to jack my car up this weekend and take a look at what I did with it, but I'm thinking it has something to do with this line not being right.

    Thanks for the input.
     
    Last edited: Sep 17, 2020

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  2. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    I've been doing a lot of digging around with the Search since I posted this last night and I found these two older posts:

    https://www.dsmtuners.com/threads/2g-awd-fuel-tank-question-about-hoses.256590/

    https://www.dsmtuners.com/threads/gas-tank-pressure-relief-hose-check-valve.246658/

    If I'm understanding correctly. It sounds like that vapor line would to run through a check valve to the charcol canister behind the front bumper on an AWD car. Mine "was" a GST so I obviously don't have that setup from the factory. On a GST gas tank everything is mounted to the tank. I scrapped my tank about a year ago after it didn't sell so I don't have any of those parts anymore. It sounds like from what I'm reading I could let it vent to atmosphere since many people remove the EVAP and charcol canister anyway. Or, I could let it vent to the atmosphere through this check valve MB925886. Again, I trashed my old GST tank so i'm guessing I tossed the check valve too, so I'll probably have to buy one.

    I gotta get the car up in the air, whatever I have it connected too is probably not something it should be connected to.
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  3. Kryndon

    Kryndon Proven Member

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    Bulgaria, Europe
    You've reached to a conclusion yourself, which is great. For what it's worth, yes, that is indeed the fuel vapor line that runs from the tank to the hard piping all the way to the engine bay, through a check valve and into the charcoal canister (if equipped). Most people, including myself with that same tank, run the check valve only and place it under the passenger wheel well, so it vents it away from the engine bay (you can barely smell fuel, don't worry!).

    Usually there's two hardlines that end near the fuel tank, one of which is for the fuel vapors, the other goes to the main pump assembly. The line that sits higher is the one for the fuel vapors. You can check that and make sure you haven't mixed them up.
     

    Street Build 4K  12

    1997 Eagle Talon TSi AWD
    13.43 @ 99.7 · 2G DSM
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  4. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    I ordered a check valve tonight from mitisubishi direct parts, I just hope I can get to the line without having to drop the gas tank shield. I don't feel like dropping the driveshaft and exhaust for a $20 part.
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  5. Kryndon

    Kryndon Proven Member

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    Bulgaria, Europe
    It's tight, but you can definitely reach the two smaller lines, they are adjacent to the fuel tank, roughly where the pump high pressure hose threads into the hard piping. The vapor line is held on by a simple hose clamp (the one which you need to squeeze).
     

    Street Build 4K  12

    1997 Eagle Talon TSi AWD
    13.43 @ 99.7 · 2G DSM
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  6. techboy

    techboy Proven Member

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    I just got an email that my credit card is being refunded as this part is now NLA. Balls. This about the 3rd time this has happened to me with OEM dsm parts. When did these cars get old ... ?? WTF
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  7. jed344

    jed344 Supporting VIP

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    Waterville, Iowa
    I ran the line back to rear of car so it vents out under at the back.
     

    1K  38

    1997 Mitsubishi Eclipse GSX
    awd · manual · 2G DSM
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  8. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    Did you have a check valve on it or just let it hang?
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  9. miguelmcv

    miguelmcv Supporting Member

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    You can let it vent to the atmosphere or ad the valve to it, if you don’t have any smog stuff, then you can even add the valve at the end of the hose, you don’t have to run it all the way to the engine bay.
     

    Street Build 763  1

    1997 Eagle Talon TSi AWD
    awd · automatic · 2G DSM

    3K  0

    1995 Mitsubishi Eclipse GST
    manual · 2G DSM
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  10. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    I wasn't planning to run it all the way to the engine bay. Since my car is not originally a GSX, I couldn't run all the way to engine bay anyway ... I don't think those hardlines exist on a GST framed car. My preference is to add the valve to it and just let it hang back there ... but I need to find a valve. If not, might have to just leave it open.
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
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  11. XC92

    XC92 Proven Member

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    Queens, New York
    FWIW, very different car, but I had a similar problem with a 2010 Kia Rio LX. Every time I filled it with gas, the engine died if I didn't keep my foot on the accelerator pedal for 20-30 seconds. Plus, when I opened the gas tank cap, there was this prominent pressure equalizing sound, like air was rushing in or out.

    I did some reseerach and determined that the EVAP purge valve was mostly likely defective, so I ordered a $20 replacement and installed it, which was relatively simple (although without hose clamp pliers it was a bit of a pain, so I purchased some since then) and voila, both problems solved.

    HTH and good luck.
     

    260  1

    1992 Eagle Talon TSi
    awd · manual · 1G DSM
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  12. techboy

    techboy Proven Member

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    Lehigh Valley, Pennsylvania
    UPDATE: Since the check valve seems to be NLA, I put the car up in the air last night and cut the rubber hose off the hardline I had it attached it so it just hangs now. I need to drive the car some more and maybe do a fill-up or two to see if it really fixes my original issue.

    I also traced the hardline I had it hooked up too so I could try figure out how I had it setup and the source of the problem. The GST (I don't know about factory GSX's) has 5 hardlines (2 brake lines, 2 fuel in/return, and 1 EVAP) that run underneath the passenger side of the car. The outer-most line is the EVAP line. That's the one I had my fuel cut off vapor line hooked up too. I traced that line to the engine bay and it leads to the EVAP purge control valve and a check valve of some sort under the battery tray. I'll be the first to admit I have no idea how EVAP systems work, and nor do I care since we're usually ripping all this garbage out. But, that's how I had I setup since I swapped the car from a GST to a GSX ... the fuel cut-off hooked to the EVAP line ... which did not play well together. FWIW.
     

    Street Build 138  1

    1992 Mitsubishi Galant VR-4
    awd · manual · Galant VR-4

    Street Build 2K  6

    1999 Mitsubishi Eclipse GSX
    13.876 @ 106.97 · 2G DSM
    Loading...
  13. XC92

    XC92 Proven Member

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    Queens, New York
    The EVAP saves unburnt gas and thus increases fuel economy and saves you a bit of money, but more importantly it keeps it from being vented into the atmosphere and further polluting it like old cars that only had open vents used to do. It's a little like the PCV & EGR that way.

    Do people actually remove the EVAP and charcoal canister on DSMs? Is that even legal?
     

    260  1

    1992 Eagle Talon TSi
    awd · manual · 1G DSM
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