Smelly gas fumes and engine cut-offs after cold start?

Thought I lucked out buying a used 5th gen with 2500 miles on it.

However, I noticed that the garage and inside of the car smells of gas fumes after leaving it in the garage overnight. The smell is strongest in rear left area of the car, and fumes for a few days before stopping (until next time I drive it somewhere and park it back in the garage, then it starts up again).

Also, sometimes the engine cuts out right after shifting into gear following a cold start. I have a few P1603 codes logged which I assume correspond to these cut-outs. There aren't any other codes logged or any active lights/faults displayed on the dash.

Any ideas what might cause this?

 

you over-pumping gasoline at the gas station, saturating canister foam filter with gasoline

 

I think @Startrek is on to something. Could there be an issue with your fuel tank, or filler neck?

 

Possible, maybe an extra squeeze but I doubt much more than a quarter gallon. Would I need to replace the evap canister in this case?

Also now that I'm taking a closer look, it looks there's an auxiliary fuel tank in place of the spare tire. There's a split in the filler neck that seems to go to the auxiliary tank. Well this is unexpected lol

 

I suspect you've found the source of your problems. I would try to find as much information as possible about the auxiliary tank, and check that everything is put together properly. It sounds like you might have a leak.

 

Yeah the vapors seem to be in that general area, and could explain why there are no codes coming up on the car computer related to EVAP problems. Something to do with the tank or tank connections itself.

How easy/hard is it to locate a specific connection point where gas vapors are escaping?

 

I really couldn't tell you. There might be some threads about auxiliary fuel tanks where you could ask. Otherwise, I might find out who manufactured the auxiliary tank, and contact them.

 

Ok I'll give that a shot, thanks!

 

I’d also reach out to we’re you got it to let them know what is happening.

 

There are such things that are called "sniffers" (this is a slang name) that are tools for finding the source of certain vapors and where they are emanating from. A good air conditioning technician would use one to find the source of a refrigerant leak. But I suspect getting your truck up on a rack and inspecting from below would be a good place to start, as liquid fuel will always leave some sort of evidence of the source of the leak.

 

When I first started reading your post, I was thinking evap issue until I got to the part about an aftermarket aux fuel tank mod. I’m betting that’s your issue. Probably why the guy sold it?

 

Hope somebody that would bother putting one in would anticipate some trouble shooting would be involved and not just throw up his hands at the first sign of trouble.

I kinda think the OP might have a cherry on top with the aux tank. How old is the vehicle? A vehicle with low miles can dry rot if it’s old. Might just be a matter of replacing hoses on the aux tank. Almost all aftermarket stuff is never as good as OEM, so I would be suspicious of any rubber involved (unless the vehicle is fairly new age-wise)

If you bought it from the dealer, tell them, and also tell them their 1,359 point inspection is a useless waste of ink if they manage to sell a low mileage vehicle that leaks fuel. Ask for money back to return it to stock. Then keep the aux tank if you want, and use the money to figure out the problem with the manufacturers help.

Where is the spare? Might want to ask they pay for one if the spare got tossed.

Oh, and pics!!! Especially of that sweet aux tank!

 

Is the aux tank made by Titan?

 

LRA. I contacted their support though and they have been responsive, so I'm cautiously optimistic so far. The tank installer agreed to leave the car overnight in their shop to see if they could reproduce the issue, so hopefully we will have a diagnosis by next week.

 

Interesting, LRA says the purge valve is connected to the charcoal canister (I guess most other cars have the purge valve in their engine bay?) It would match the general area where the fumes are strongest, the rear left of area of the car.

Googling around it sounds like a purge valve stuck open could cause both the venting of gas fumes I'm getting, as well as the engine cut-outs right after startup. As I understand, the car's computer expects the EVAP system to provide some captured gas fumes for combustion and the demand is highest around startup. But if those vapors are being vented to atmosphere, then the air/fuel mixture is too lean and cause the engine cut-outs. I've had some rough idling too which I understand is another sign of the same.

However this turns out, it feels empowering starting to understand how this stuff works! Really liking the community here

 

Wow. Yeah that’s good to know information. The complexity of these things is crazy. Once that issue is worked out you will love that tank on trips! I’m jealous. Just curious- where’s the spare tire?