Stall after filling up

For as long as I can remember (at the very least, 6 or 7 years). My 2005 Elise has complained whenever I refill the tank. For a while, it would fire up okay (not great, just okay) when getting fresh gas and then try to stall after leaving the gas station when sitting at the next light. Different gas stations, different states, fairly repeatable behavior. 

The car then sat for the most part of 4 years while I rebuilt it, and I have now been driving it relatively consistently for the last year and a bit. Prior to the rebuild, it transitioned to stalling right after it lit off at the gas station and then would be just fine the rest of the time. It seemed like a natural progression of the original issue. It would also hunt at idle due to an O2 sensor issue once warmed up, but the problems were different enough that I have reasonable confidence that I can tell they were different problems. 

I fixed the O2 sensor about 14 months ago and tidied up the evap/charcoal system, so it *should* be in the factory config. Previous owner did some partial removal of things, and I hoped that was the reason for the stall, but nothing has changed. I think I am far enough away from the O2 sensor problem that I can rule that out as well. I can see no other symptoms of any other issues, and I had been running a wideband the whole time, too. AFRs have always tracked pretty nicely. My main culprit is still the evap system since I don't have a great understanding of what all it is trying to do and when, but I do think it has something to do with fill-up. Is there anything in the evap logic that opens a solenoid only during cranking/idle with fresh fuel? If so, that's my main suspect. 

Can anyone with experience offer some insight?

I don't suspect the fuel system since I have no issues with cold start or hot start (as long as it doesn't have fresh fuel).

I don't suspect it is debris getting sucked up since I'd expect that to be less predictable and over a broader set of conditions. 

I don't suspect the fuel trims since I have had the system when refilling with the same brand, and the stall is immediately after it fires off. You can hear it light then die almost like a cam phaser solenoid issue, but again, I'd expect cam phaser solenoid failure to not only happen with fresh gas. 

Not gonna say I'm familiar with those cars but tough start after fueling I would be looking at the purge system possibly in connection with the canister that was modified. 

As far as I have been able to tell, all components are present and unmodified. The previous owner had disconnected some hoses and solenoids here and there (probably when installing or removing the supercharger that was removed before I bought the car). I would occasionally get a CEL related to those changes and saw no performance intent of what he did, so I put it all back. No CELs since (knock on wood). Strangely, I also had the stumble after fill-up prior to putting everything back together, and I didn't document it well enough to know which part(s) are still connected the same as they were before. 

I'm also assuming the system is broadly the same as any early 2000s OBDII car since nothing looks terribly special. The solenoid is from a Chevy or a Ford truck, that I do know. 

My 911 did the same thing.  It was an EVAP/purge problem.  Never had a code, but it would stall/hard start after fill up and sometimes after being parked for a few minutes and restarted.  It's been a while, but I think it was the purge valve.

Purge valve is stuck open, applied on at the wrong time, or something is plumbed wrong.

Pull the hose to the canister off the purge valve, idle the engine, see if its sucking.  Yes?  Unplug the wire.  Still sucking?  Change the solenoid.

Evap/purge valve behavior seems likely to me, too. filling the tank replaces air volume with fuel, and that air and fuel vapor mix has to go somewhere. If the valve is open during fueling, you might be pushing vapors through the system resulting in a rich stall soon afterwards. Odd that sometimes it happened somewhat far from the station though; I'd expect this on first start after fueling. 

Most of those evap solenoids are normally closed that I've seen - no flow when not powered. They also shouldn't flow with the engine off, or at idle in most cases.

As far as ECM parameters after fill up, the LTFTs don't change. STFT is a short enough rolling window that it doesn't matter that they reset. The only thing I can think of that typically changes is the fuel octane scaler. They will often reset after a fill up, so if you had high knock counts pushing you towards running on the low octane tables, after a refill you'd be back to the base high octane ignition map until knock sensing re-learns the map scaling percentage. 

In reply to gearheadE30 :

Yeah, not a ST/LTFT issue for sure. 
It won't be the knock offset reset since, after stalling, it starts right up. Vapor theory makes the most sense, but wouldn't that mean the solenoid is always open? Would that result in symptoms of a vacuum leak? Or does the fuel tank seal well enough that it doesn't?

Is the charcoal canister filling with fuel?  I have seen issues with tank vent lines causing the canister to fill up resulting in rough running & stalling after refueling.  I would try plugging the tank vent line to the engine & seeing if the issue still occurs 

I've got a hard start after fill up, and only when warm.  Mazda3.  Car is also throwing a P0442 -  emissions evap system slow leak.  I've replaced the easy stuff - gas cap, purge valve, and so it's probably the purge valve (which is under the car and requires dropping the subframe.  What genius did that design?)  One of these days I might get around to fixing it.

Do you have a scan tool and smoke machine?  See if you can control the vent valve to closed. Add smoke from purge valve in the direction of the tank and check for leaks. See if you can control the pump and force it to run.  It may have a self test but over the years I've learned not to trust them.

jwagner (Forum Supporter) said:

I've got a hard start after fill up, and only when warm.  Mazda3.  Car is also throwing a P0442 -  emissions evap system slow leak.  I've replaced the easy stuff - gas cap, purge valve, and so it's probably the purge valve (which is under the car and requires dropping the subframe.  What genius did that design?)  One of these days I might get around to fixing it.

My Mazda five did similar things, and no one wanted to work on it. Three locations referred me to the dealer. I didn't want to mess with it myself, and I was determined never to go back to the dealer. The dealer had tried to sell us a transmission replacement for something that I resolved with a few drain and fills in a couple of hours. 

I was ready to take a shot at it, but when the Mrs suggested we trade it I didn't have to think twice. 
 

On our odyssey it was the evap solenoid. I had replaced the definitely broken Honda part with a "parts store" one and it cleared the emissions code but would give a long crank after fill up if I went to a full tank. If I estimated the fill a bit under full it would be fine. The stupid thing bench tested fine, but totally fine with an OE Honda version. 

My Civic has a bad EVAP solenoid, and unfortunately for me, it was the one that was discontinued and located close to the gas tank. Local shop traced the issue via smoke test, but could not find a new solenoid, and that one was discontinued so they found a used partb but it still gave me CEL issues. I was doing my best to keep the stock ECU on my Civic, but the CEL forced my hand to switch to Hondata. CEL went away, since it doesn't check for it. But did have the stalling issues on filling up. Messed with the settings on Hondata and it no longer stalls

That's the weird thing. I'd expect a bad solenoid to be more of a nuisance more often than what I'm actually getting it is strictly only (noticeable) after filling up.