Gas tank puking?

[Warfang]

So I just took a long drive to LosAngeles. Stopped at 2 gas stations and noticed something semi disturbing. Seems like the gas tank puked some gas up and rested in the inner lip of the gas recepticle. It smelled like gas, but it looked reddish-brown, and about 1-2 ounces worth. I soaked it up with some paper towels both times and the car runs fine. Is it the pressure on the gas cap? I have one of those after market key-locked gas caps.

Questions:

1. Where does this come from and why?
2. Does it damage the engine in any way?


Off topic things I've noticed during the drive:

1. The Viper LOVES to be driven. The longer you drive, the better it drives (more responsive and power)
2. At 80mph in 6th gear with stock gearing... I got well over 20mpg (usually around 10mpg)!
3. For 400 miles, I saw 1 Aston, 12 vettes, and lost count of Mustangs... no other Viper.
4. Even when not speeding, people pull over to the slow lane to let you pass by.

 

[Burntrubber]

The only time mine did that was when I filled it when the car was running, the only reason it why I did that because it was sitting for 6 days and barely started (battery) so I didn't want to chance it dying at the station.

 

[kcobean]

Your drain is blocked too huh? No idea how you'd be getting blow-back from the gas tank, particularly discolored like that. Clearing that drain line is a pita because apparently you have to pull the inner fender liner.

 

[Warfang]

Your drain is blocked too huh? No idea how you'd be getting blow-back from the gas tank, particularly discolored like that. Clearing that drain line is a pita because apparently you have to pull the inner fender liner.

The drain is outside of the recepticle (if that's the right word). When I take the cap off and look inside (where it's aluminum), the gas sits on the inner lip where about 1-2 ounces can sit without draining back into the intake.

I guess I should go take some pics.

 

[Warfang]

The only time mine did that was when I filled it when the car was running, the only reason it why I did that because it was sitting for 6 days and barely started (battery) so I didn't want to chance it dying at the station.

Not sure if we're talking about the same thing. The gas didn't "puke out" at me. When I take off the cap, the colored gas is just sitting there.

 

[kcobean]

The drain is outside of the recepticle (if that's the right word). When I take the cap off and look inside (where it's aluminum), the gas sits on the inner lip where about 1-2 ounces can sit without draining back into the intake.

I guess I should go take some pics.

Oh, I gotcha. Pics not necessary, except I would like to see the color of the fuel....that's very curious.

 

[Warfang]

Oh, I gotcha. Pics not necessary, except I would like to see the color of the fuel....that's very curious.

It looks like watered down coffee. It could've only come from the tank itself (or possibly the cap), and this is after multiple fillings in a short period of time. Under my regular use... 15-45 minutes drives, 4-10 times a week... I never see this during fillup. I can only conclude driving prolong periods is causing this. This is also the first time I've used 6th gear for long durations.

Any of the supergeniuses with ideas?

 

[RTTTTed]

Not sure about the "supergenius" part - but did you say it pukes gas and runs better with longer drives? Just once or each time?

First thing I'd do is try a new gas cap I traded a fellow VCA member during a long drive. See if his Viper slows down, pukes, etc. and if yours still does it or not. Perhaps switch with a equal year Dodge pass. car? Hopefully YOUR Viper goes faster and doesn't puke with the other cap.

I looked in my shop manual and it mentions the charcoal canister and a EVAC tank at the front of the car. It also mentions the Leak Detection System pump, etc. Any engine codes?

Ted

 

[Warfang]

Not sure about the "supergenius" part - but did you say it pukes gas and runs better with longer drives? Just once or each time?

First thing I'd do is try a new gas cap I traded a fellow VCA member during a long drive. See if his Viper slows down, pukes, etc. and if yours still does it or not. Perhaps switch with a equal year Dodge pass. car? Hopefully YOUR Viper goes faster and doesn't puke with the other cap.

I looked in my shop manual and it mentions the charcoal canister and a EVAC tank at the front of the car. It also mentions the Leak Detection System pump, etc. Any engine codes?

Ted

No codes... at least no "check engine" lights. Does the charcoal canister and EVAC tank connect to the gas tank? I have no idea.

I'm not sure if the cap/puking had any effect on the power. It just seemed like the car enjoyed being on a endurance run... probably why it took LeMans. But I think I will buy a new cap at a parts store and see if there's a difference.

 

[RTTTTed]

Since you're sure you have gas coming past the cap to the outside the cap obviously leaks. Although I have read threads where bad gas caps also threw codes. My 98 GTS had an aftermarket locking gas cap, but everything worked great.

Yes the EVAC tank is the gas tank vent system. It collects vapors and opens to the intake when starting the engine. Part of the emmissions. The filler neck also has a vent that goes into the top of the fuel tank.

Sorry I couldn't be more help though.

Ted

 

[2snakes4us]

The filler neck also has a vent that goes into the top of the fuel tank.

Here is a shot in the dark, could you have topped the tank off to a point where the"Vent pipe" filled up with gas and washed off the vent hence dirty gas? and changing altitude (grapevine)and outdoor temps cause the gas to expand and cause the tank to purge?

 

[Warfang]

Here is a shot in the dark, could you have topped the tank off to a point where the"Vent pipe" filled up with gas and washed off the vent hence dirty gas? and changing altitude (grapevine)and outdoor temps cause the gas to expand and cause the tank to purge?

I had the same issue before and after grapevine, so that probably isn't the deciding factor, but could be one of the contributing ones. I'm not exactly sure at what point I topped off. I just let the pump stop when it thought was full and I didn't put in a drop more. Outdoor temps might be possible, although it was an even 70f yesterday... could be just the duration.

Driving back Monday... I'll alternate gas caps and see if there's a difference.

 

[Warfang]

Since you're sure you have gas coming past the cap to the outside the cap obviously leaks. Although I have read threads where bad gas caps also threw codes. My 98 GTS had an aftermarket locking gas cap, but everything worked great.

Yes the EVAC tank is the gas tank vent system. It collects vapors and opens to the intake when starting the engine. Part of the emmissions. The filler neck also has a vent that goes into the top of the fuel tank.

Sorry I couldn't be more help though.

Ted

No... the leak is inside the cap. The brown gas is settled at the lip inside the aluminum neck right before the opening. The gas never escapes the cap.

 

[Warfang]

OK... I took pics, and realize the leak is OUTSIDE the cap... meaning the gas escaped the cap. It seems to leak out, and while some goes down the drain hole, some also roll down the side of the car. Any comments?

 

[viper spray]

Looks like a plugged drain tube is spitting up old gas and water...........

 

[Warfang]

Looks like a plugged drain tube is spitting up old gas and water...........

Doesn't the drain tube start at the hole underneath? The puke seems to start inside the cap and not from the hole below.

How hard is the fix and how safe is it to drive in this condition for 400 miles?

 

[kcobean]

Doesn't the drain tube start at the hole underneath? The puke seems to start inside the cap and not from the hole below.

How hard is the fix and how safe is it to drive in this condition for 400 miles?

Yeah, that would be nearly impossible for that to be coming up from the drain tube (it would somehow have to climb up the filler neck to get inside there.) I have no idea what that could be, I've never seen gas that dark, except the stuff I mix with 2-cycle oil to put in my ****-whacker. You're not running a two-stroke in your Viper are ya?

Curious to see what the answer to this mystery is...perhaps call Mr. Tator and see if he has any ideas?

 

[dave6666]

OK. I'll take a stab at it...

Gasoline has a vapor pressure to the point where in hotter weather it used to be a concern with it boiling in old carbureted engines causing vapor lock. Of course that has been addressed with fuel injection. But still today, the stuff sits in your gas tank and gets warm. Quite possibly accelerated by the mechanical components like the diff and exhaust below it.

It evaporates into a vapor which travels up the fill pipe and then condenses back into a liquid, as the cap area is far enough removed from the tank it is cooler, allowing the vapors to condense.

If the gas cap were to leak these vapors would make it to the area you have pictured, but since that area is gasketed the vapor would not escape but condense and form liquid.

Why is it dark? Well, the gas door seal is not 100% positive, and some evaporation takes place turning the condensed gas vapors into gum and shellac like residue, which is darker.

My theory of course is only supported by a leak in the gas cap area, whether the cap or the filler neck is to blame.

An alternative guess is you go around left hand turns way to freaking fast splashing gas back up the fill pipe. Same leaking cap scenario though.

 

[viper spray]

Try a different gas cap , fill her up and drive for a while. After looking at the pic it looks like the cap is bad and may be leaking.......

 

[Cobraken]

California gas

 

[dave6666]

Try a different gas cap , fill her up and drive for a while. After looking at the pic it looks like the cap is bad and may be leaking.......

Oh sure. Give an easy explanation.

 

[Warfang]

drum roll please.....

Got new gas cap and no more leaks! Still a little baffled about the color though. It could be airborne crap or Dave's shellack theory, but what if it's IN my tank? Might siphon some gas out to check tomorrow.