sp0da

Have you taken a look at the hoses/connectors on top of the sending unit to see if there are any cracks/leaks with those lines? Our cabin air filter is *roughly* in the same area, (as Macster pointed out in post #4 it might be pulling in some fumes), so it might be worth a look if you haven't checked already. It only requires removing the battery and tray to check and checks off a few troubleshooting items in the process.

Other than that, I got nothing. :/

black04

I think the point is...You never know what will come loose, start leaking, rubbing and do what, until you see it. :-)

NaroEscape

So...fill #4 update...we're back to the same original problem. Can only fill about 1/2 gallon, then 1/10 gallon at a time. Not only annoying and time consuming, but extremely embarrassing. "Hey look at that expensive car...can't even put gas in it!"

I'm at a loss...

Macster

Well, I'm not sure I can be of any more help but if you will bear with me I'll give it a try.

I believe you have replaced some hoses. I believe you have apparently addressed the fuel smell in the cabin. But as I like to say with cars there are always 2 problems, unless there is just one or 3 or more...

I think you have the classic two problem, err problem.

I didn't do a thorough (re)read of the thread and I apologize in advance if I missed this, but have you checked the canister to be sure it is not full of fuel? Have you checked that the canister contents are not loose? As the fuel tank fills vapor must be able to freely flow into the canister so it can be absorbed by the activated charcoal. If the flow of vapor is in any way impeded...

I know this is a repeat but I think it bears repeating: As the tank is filled the tank vapor should flow up from the tank through a line to the canister. If this line or a connector or the canister has any restriction the tank doesn't vent properly and this causes the gasoline nozzle to detect a "full tank" condition and shut off. Based on what you posted I think this is happening.

That's one possible explanation.

There can be another. I have to wonder if fuel is being introduced from a port high up the filler tube where the canister connects or is the nozzle shutting off because fuel is backing up from down below the nozzle backing up like the tank is, well, full?

If the latter this could be due to a rollover valve having somehow failed, gotten partially stuck, jammed nearly shut, anyhow something has (possibly) gone wrong with the roll over valve..

One might consider trying to fill the tank, at least partially, by pouring some gasoline from a gas can into a funnel and carefully viewing the fuel as it flows down to confirm that it drains down promptly.

But if you go this route you do so on your own. As I said above fuel and fuel vapor are dangerous and vapor is the worst of the two. Just a spark with a cloud of vapor around and the car could be in flames or worse you. The vapor can collect around/in your clothing and well, you just don't want to run this risk.

When it comes to possibly messing with liquid fuel or fuel vapor I have to point out that maybe it is time to call upon a professional.

While I admire your persistence and the progress you have made there comes a time when one needs to consider turning this over to a professional tech. These modern cars with these vapor recovery systems and the support hardware to allow the DME to perform various tests to check for small or large leaks are pretty complex. The techs get exposed to these systems at a level of detail we can only imagine so their understanding of what can go wrong is much better and how to figure out what is wrong is much better, too. They know where to look, how to look for a problem. Plus there is good old experience. The chances are your car's problem is not the first time this problem has been dealt with.

So you might consider bringing the car to a qualified tech for his professional diagnosis.

NaroEscape

Macster,
thanks again for the response. I'll address your comments individually:
- When I replaced the three valves, I took out the canister and confirmed that I could blow through each port very easily, so there was no blockage that I could detect.
- where is the rollover valve you speak of?
- since I also race another car, filling a tank with funnel is normal for me at the track, so I'm not concerned there. I may try that.
- professional diagnosis - that's where this all started. I took it to my local independent and we disassembled the entire system to check everything. At that point, we replaced the carbon canister. The first couple fill ups after that, everything worked fine and I thought we had it fixed. then on about the 3rd or 4th, it got instantly worse as it has now (can only fill 1/10 gallon at a time).

What I can't figure out is why does it work better after doing any work, but gets worse after a few fills? What's allowing it to get better for a little while, then stop working? If it didn't get better at all after we replaced the canister, or valves, or anything, I could understand that we didn't find the problem. But it seems that we find the problem, only to have it come back.

Macster

The rollover valve is part of the fuel filler tube. Not sure where it is located. It may be the metal flap that is pushed open when one inserts the fuel nozzle pipe into the fuel filler opening.

Maybe you need another professional's diagnosis? Dealer techs see a number of cars and chances are your's is not the first one to manifest this behavior.

I don't know why the symptom is gone after work is done on the car then gets worse after a few fill ups. But to the right tech I have to believe this info would have a light bulbl glowing over his head.

NaroEscape

I need to bring this thread back up for a few reasons:
I chased this issue for months, eventually replacing EVERY SINGLE vent valve, carbon canister (twice)...everything. Even a couple hoses. Even replaced the vent valve at the top of the tank (no easy task since you can barely see it let alone get to it). did all this 6+ months ago and since then...all has worked perfectly. Fills all the way up on one shot, like any normal car. Excellent...

Then we left for Daytona this past Friday and stopped for gas along the way...and...oh no. I won't fill. WTH?!?!? Same as before...0.1 gallon at a time, then it sloshes out the fill neck. And I mean SLOSHES, like "get out of here" throws it out the neck with force and all down the side of the car. Again...WTH??? it's been perfectly fine for >6 months and 7000+ miles....So once again, its fill at 0.1 or less gallons, stop, little fill, stop...15 minutes to fill the tank. No clue. There's NOTHING left to replace!!

Then I thought "well..maybe its the long trip creating pressure or something". So we let it sit overnight and got fuel first thing when we got up. Nope, same issue.

I suspect that somehow, the vent hose off the tank to the carbon canister is blocked somewhere, somehow. But how? or if there is fuel in the canister causing blockage, how did it get there?

I am at a complete loss. Talked to a few experts and dealer mechanics I know, all said 'replace this or that' and when I say they've been replaced...they too are at a loss.

<sigh> first time my wife actually said "we need to sell this, its starting to not be a fun car anymore..." She loves the car (its technically hers)..sad to hear that.

177mph

Just to get everyone up to speed - what mods have been done to the car? Is there any sort of battery cutoff switch by chance?

NaroEscape

Gofishracing

Any update?

NaroEscape

christallon

https://rennlist.com/forums/996-gt2-...is-thread.html

Just in case you did not see this thread from 2016. This guy also had a hell of a time tracking down the culprit. Good Luck!

christallon

Oh, I just saw you were the last post on that old thread by Kgorman. Sorry about that.

StephenB

Sorry to hear. Two things I would check based on my school of hard knocks: 1) New parts can go bad and one of the new valves may have failed prematurely; 2) The wiring harness may have an intermittent fault (the most difficult to diagnose)

Murphy can dog your days and haunt your nights trying to chase these down. BTDT on similar issues with vehicles in the past.

Anthony Lovero

I had this issue awhile back as well. Would get fuel smell after some drives on a hot day. I took the right front fenderwell out and inspected all of the plastic vacuum lines that are around the canister. I found one of the fittings connecting two pieces of plastic vacuum line looked to have some dust accumulated around it indicating a leak. I unplugged it (and all other lines in that fenderwell), cleaned the dirt and debris off of everything, and re-terminated them. I have not had the problem come back since.

Also, when you push the little door in the filler neck below the fuel cap all the way open, you should hear a solenoid click. I think that opens a vent line up to allow proper tank fill. I would also verify that the component is working and is making a click when you open the filler neck door (as would happen when you insert a gas pump nozzle into the filler neck)

Good luck! Time and effort and I'm sure it will get sorted out.