Gas smell, i've had it with this gremlin

[Jiggerachi]

I've got a gremlin that comes back every summer, this time it showed up much earlier, which makes me think it's going to be even worse this year once it gets really hot.

Only happens when i've been sitting in long traffic on a hot day. Smells very strong like ethanol, not raw gas. It's so strong it's almost intoxicating, it'll give you a headache even with the top down.

I've been reading on Miata.net a lot lately, but can't find any real data. I read a post on Miata.net where a guy found a clogged gas relief valve under teh package shelf carpet. I'm not sure because I smelled the carped back there and didn't smell anything, but i'm going to pull the valve in question and clean it before the roll bar install while i'm back there.

I pinpointed the general area, and it seems strongest under the hood around the charcoal thingy. I inspected the hoses and couldn't find any that were cracked, and couldn't even find the direct source, but only there were VERY STRONG wafts of ethanol smell every now and then coming from somewhere in that general area(not a steady smell, just wafts).

I also read on M.net that if you top of the tank frequently it can 'flood' your charcoal can??? But as always on that site only heresay and generalizations. Either way i'm a big offender on that, I top off frequently to round off the number at the pump for some reason.

Anyone have a spare charcoal canistor laying around that I can test? Any ideas where to go from here, i'm completely ignorant of any emission systems, I have no idea where to start, and i'll have my 1 yr old son in the car in traffic pretty soon, i'm sure huffing gas isn't too good for a toddler's brain cells.

[Titus]

Stop topping off and I bet the smell goes away.

[Jiggerachi]

^Ok, dangit, it really bugs me for some reason to pay $24.73 instead of an even $25. I'll have to live with it I guess.

What exactly is the problem with topping off?? Is it blocking some relief valve? Not saying you're wrong, just curious. The problem happens regardless if the tank is 3/4 full or on E, always stinks when i'm in traffic. That's what makes me wonder if the charcoal can is dead or full of gas or something. And the heat makes me think it's a pressure thing, which would make sense if something was clogged.

[Titus]

As I understand it, you want a little air space in the tank. This way, when it gets hot and the gas expands, only air/vapors are pushed out the pressure release to the carbon canister. If you top off, you can end up having gas go out the pressure release and in to the canister.

[Jiggerachi]

Hmm...If I get time i'll pull the can and see if gas pours out or anything strange.

[Titus]

http://www.epa.gov/donttopoff/

[cwisenheimer]

Plus, if you top off, the fuel level can be high enough to be above the tank itself and into the filler neck where there are joints that can leak, especially if gas is sitting in constant contact rather than just flowing past. Just don't.

[juxt3r]

I miiiiight still have the canister from my '90 if you really want to try changing them out.
...you know, just to see.

[Jiggerachi]

^Yea I don't know. Might be worth a shot. If the theory is correct I may have been pumping raw gas through the vent system and into the charcoal. It has to be more complicated than that, though. I dont think that stopping my environmentally-evil topping off habit will fix it in and of itself. Something has to be venting the pressure outside of what, from what I understand, is a closed system. Anyone know if the can has the ability to drain itself, is that what the tube underneath it is for?

A possibility of dumping raw gas through the system has to have lasting effects, though. Now that I remember when I was pulling the clutch I remember smelling some nasty gas smell when removing the slave cyl after the car had been parked for almost 20 hours. Maybe whats inside the can is clogged and reaks of gas.

But it's worth a shot anyway. Actually probably easier to just unplug the wires and loop them for a test, bypassing the can altogether. Whatever I try it will be tough testing it since it only happens in the semi-rare occasion i'm stuck in traffic for more than an hour on a hot day.

[HudsonHawk]

Yes the canister will drain if it fills with liquid.

How it normally works is at cruise a vacuum valve opens and draws the vapors out of the canister and back into the intake. If its full of liquid there is a valve that will open and release the liquid which would explain the strong smell of gas. I had this happen right after I rebuilt my CJ and added the fuel injection. I was on a slope and flooded the charcol canister with fuel. There was a nice stream of gas pouring on the ground. I installed a shut off valve for the vent line after that so I would not have that problem off-road again.

[POS Racing]

Stop topping off and I bet the smell goes away.

Let us look deeper when the car reeks of gas what does the fuel gauge show? Is it always full when this gremlin appears??

[Jiggerachi]

I can't remember exactly, it happens so sporatically, but I know I didn't fill up the last few times it did it. It wasn't empty either. I would assume somewhere around 1/2 a tank, probably. I remember it not having any relation the last few times, it would happen at 3/4 or 1/4 it wouldn't matter **that I remember anyway**

On a side note, my gas mileage has sucked really bad lately. I though it had to do with putting on 15x8s on and driving aggressively. The smell problem is nothing new, however. My crappy gas mileage has only been in the last year or so, probably unrelated.

[Jiggerachi]

Check this thread out on Miata.net.

http://forum.miata.net/vb/showthread...as+smell+valve

It's about the only thing ive read with actual results on what appears to be a fairly common problem with Miatas. Thing is I thought it would be venting into the package tray carpet but no smell up there, the fumes are definitely coming out from under the hood and leaking into the cabin. In the next week or so I'm going to pull the panels back there and clean out this valve. If it was plugged it might be sending too much pressure to the charcoal can or something wierd like that. It's one thing to check anyway.

[sammm]

Can you hear your gas cap release pressure when you open it?

[Jiggerachi]

Sometimes yes, sometimes no.

[POS Racing]

Check out post #4 on this link - http://www.dfwmiata.com/showthread.p...l=1#post213302

Looks like that Jigger kid may have figured out something.

Maybe try cleaning out that valve???

[Jiggerachi]

^Hahaha. Yea I found this last year, crawled back there and smelled around the carpet with no smell so I thought the valve was ok. I forgot all about everything with the cooler weather. Now that it's back I realized I shouldn't be so lazy.

Problem for me is on my car, those panels and screws are all rusted over, the screws basically crumbled when I tried to remove them last year. I bought new panels and screws at that time, but it's going to be a pain to remove the rusted crap.

[Rob®]

PB Blaster, or ideally, Fluid Film. You might get lucky and just snap the heads off, allowing you to remove the panels and get the remaining bits out with Vise-grips. If not, have fun with an extractor bit.

[POS Racing]

^Hahaha. Yea I found this last year, crawled back there and smelled around the carpet with no smell so I thought the valve was ok. I forgot all about everything with the cooler weather. Now that it's back I realized I shouldn't be so lazy.

Problem for me is on my car, those panels and screws are all rusted over, the screws basically crumbled when I tried to remove them last year. I bought new panels and screws at that time, but it's going to be a pain to remove the rusted crap.

What I find interesting is your original post about the gas smell was posted 1,959 days ago or 5 years, 4 months, 1 week, and 3 days have past and your still asking about it!

I'm not sure after this much time if this still can fall under the lazy heading.

Original post - http://www.dfwmiata.com/showthread.p...t-smell-lately

[AlanP1964]

My 95 did this toward the end of the hot part of the year last year. It's just a real strong, pungent type of smell. It is definitely a gas smell but different than just smelling plain gas. Hard to describe. Mine definitely is not from the parcel shelf. Mine also is just mixed amounts of gas in the tank. Can't say for sure if it was 1/4, 1/2 or full etc just that it would do it when it was hot out and after I drove for a while, like on my ride home from work.