Ongoing fuel system problem since new...now worse since we left on trip...

[garymunson]

Anyone have a similar problem? After we got our new Volt, the check engine light came on the 2nd time the gas engine ran. Onstar diagnosed it as a 'low purge flow' in the emission system and set up an appointment at the dealer. Their diagnosis was a bad purge solenoid and we had to return the following week once they received the new part. It was installed and I was warned 'not to overfill the gas tank' as the purge system was flooded with gas (we had not had to fuel the car since purchase at that point). Again, the 2nd time the gas engine ran, the light came on. We returned to the dealer for the 3rd time and they again diagnosed a bad purge solenoid and ordered another. Again I was warned about overfilling although we had yet to visit a gas station for the first time. We had a trip from Reno to Portland planned but since we were told the purge issue was not a safety issue, just an emission one, driving with that code was not a problem. The part did not arrive before our trip so we planned to have it replaced on our return. We planned to leave yesterday (Sun, 7/15/12) so Saturday evening we stopped to fill the tank for the 1st time. The weather was cool so we left the doors open while we added a measly 5 gallons and got back in. I thought I smelled gas in the car but my wife, who usually is more sensitive to that sort of thing, didn't. Sunday we drove up through California and into Oregon where we needed to refuel. This time it was hot and we closed the car up as we refilled. When we went to get back in, the gas smell was overpowering, like someone spilled gas in the car. We opened all the doors and the smell was soon gone and we continued on until we got a motel for the night. I was unable to see any evidence of liquid fuel anywhere so my assumption is that the problem centers around the system that vents fuel pressure when you refill. The Volt is the only vehicle I'm aware of that maintains fuel system pressure at all times (except during refill) to protect fuel quality between fillups (that tend to be far apart). My reasoning is that the purge issue and the smell are related. I plan on calling Onstar once I'm on the road this morning and have them set up an appointment at the Portland Chevy dealer and let them have a crack at it. Although the smell goes away, I'm not entirely comfortable driving the car now. I'm thinking the fuel pressure system must be intact or the computer would issue a code for that since it must monitor pressure so it knows when to allow the fuel filler door to unlock. Maybe some sort of 'swapped vapor line' issue? Anyone know where the fuel system pressure gets vented when it's refueling time? I would think it has to be through some sort of charcoal canister since emission laws wouldn'y let you dump it to the air. I'll keep everyone informed..Gary

[Bob_Livonia]

Anyone know where the fuel system pressure gets vented when it's refueling time? I would think it has to be through some sort of charcoal canister since emission laws wouldn'y let you dump it to the air. I'll keep everyone informed..Gary

Correct about the charcoal.

I haven't had the problem, but I think I remember seeing a one or two on the forum. Perhaps the dealer person overfilled it, assuming you had a full tank a gas when it was delivered. A warning well heeded for those (not you) who top off into the expansion room at the top of the tank. I always stop at the first or second time the nozzle clicks off. The little bit of extra gas one might put in is not worth it.

I am confident the dealer will get to the root cause of the problem, even if they need some help from Chevrolet. Chevy (and your Volt advisor) would be highly supportive of that if needed. I would think they would provide a free loaner car, particularly if it takes a few days to make it right - if it was my Volt, I would prefer not to drive it until fixed. All vehicles are subject to the evaporative emissions controls (a 1960's car produces more emissions just standing and not running than a current model car produces running). The Volt does have additional fuel tank pressurization designed in to keep the fuel fresh even if it is not used for months, which makes it a bit more complex and susceptible.

[Murrcar]

You are correct. The smell is related to the purge valve not working. The fuel vapors in the tank arecollected in a EVAP canister that is filled with charcoal.
I am a GM engineer who works with the EVAP system diagnostics.

The engine burns the vapors when it runs. If the purge valve is inop then the vapors cannot be purged from the canister. After the canister is full (it only takes a couple of fuel fills) then the vapors excape and you can smell gas. If you do not get the purge valve fixed the canister could fill up with liguid gasoline. If that happens then it will have to be replaced. This is not a saftey issue! The system is vented when the engine is running. It does not affect the fuel pressure. The EVAP system is a very low presure system, not the high presure system that supplies fuel to the fuel injectors.
One tid bit, most people get an EVAP code when they forget to tighten the fuel cap. It takes only a .020 inch diameter hole to set the small leak code(two weeks on a normal vehicle to set the cose). It takes a .090 in dia hole to set a large leak, sets in 2 drives.

Bottom line do not worry about driving the car. But get it to the dealer as soon as it is convenient. There may be some other issue with the EVAP system since you already had the purge valve replaced.

The Prius uses a similar sealed fuel tank system.

On conventional ICE the EVAP system is vented al all times, except when the system checks run.

[garymunson]

My concern on our trip is the intense gasoline smell inside the car when it gets refilled. I worry that even the door light switch could ignite the fumes.

[DonC]

Murrcarr is saying it is NOT a safety issue because everything is vented. I believe that, but, for peace of mind, you may want to confirm this with your Volt Advisor. I also believe we have seen this or a similar issue at least once before when the dealer overfilled the gas tank, but I thought there was some design change that now prevented this. You may want to search for that thread.

[Steverino]

Let paragraph breaks be your friend, garymunson.

http://gm-volt.com/forum/showthread....r+overfill+gas

[garymunson]

My question might better be 'why is the closed car filling with gas fumes?'. It seems to me the vapor lines should not be inside the car at all. Since the check engine light came on after the repair and before I ever put gas into the car, It would indicate to me that the purge solenoid probably wasn't the initial problem but the car computer incorrectly reported it because of some issue that has the 'fumes in cabin' issue in common with something else as yet undetermined. Even if the solenoid was bad (2 in a row??), would that allow fumes to enter a closed-up car? Doesn't seem like that should be the case.

[jegund]

Try de-presurizing the fuel tank, not at a gas station. Many time previous cars overfill spilling gas on the pavement below your car and opening the door will fill your car with fumes. Then you can at least rule that out.

[cab]

The gas smell is a BIG concern here folks and probably a clue. The fuel pump and lines go in through the top of the tank on most cars. If the car smells strongly of gas when filled it is often because the fuel is essentially up against the "cover" and LEAKING past the seal on the cover or the cover is cracked. I'm not saying that is definitely the case, but given that I have experienced this on 2 separate cars (one my own fault when I did not tighten said cover enough on my wife's 530i - the other a 95 Maxima where the cover/sending unit combo was cracked and weeping fuel) it is a definite possibility.

[Murrcar]

Some more on EVAP system diagnostics. All modern cars have a fuel system presure sensor in the canisteror the fuel tank. When the engine is started the system is opened, vented. After the engine warms up the vent is closed and the purge valve opened. If the system does not build a vacumn in a specified time then there is a leak in the system, the vent did not close or the purge valve did not open. If you are having oder issues, then the most likely problem is the purge valve not opening OR a leak in the system between the valve and the canister. The dealer may have caused the leak when they replaced the valve. Any leak large enough to set the code would be large enough for you to smell in the vehicle.

If you ever get around an older vehicle, pre EVAP emissions. they all have fuel oder after you fill them or when you park them in an encosed building.

This EVAP issue will not and can not have any affect on your engine. The door lock cannot light the fumes. It takes a large spark or an open flame to set gas on fire. And the air/fuel ratio has to be in a very narrow band.

By the way the Prius also has the closed fuel tank system.