Gas smell, i've had it with this gremlin

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.

Stop topping off and I bet the smell goes away.

^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.

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.

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

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

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.

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

^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.

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.

Quote:

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Originally Posted by Titus

Stop topping off and I bet the smell goes away.

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

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.

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.

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

Sometimes yes, sometimes no.

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. ::Clown::

Maybe try cleaning out that valve???

^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.

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.

Quote:

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Originally Posted by 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.

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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

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.

It went away after that post for 3 or more years. I chalked it up to funky gas. That smell was coming out of the exhaust anyway. Wether it was the same root cause or not, it came back with a vengance last summer then promptly went away again. Now it's back again and now and I need to fix it for the kid.

Another note, if you must know, is previously it only happened on very hot days when I get stuck in traffic, now a days I hardly ever get stuck in traffic since I take back roads to work and only use the Element if i'm taking the new family somewhere. I've been stuck in bad bad trafic only a handful of times in the miata in recent years, so if there was a problem I never smelled it, or smelled it rarely enough to not care all that much.

Pretty soon, though, my wife will be commuting all 5 days again so when I get a roll bar i'll take half of the kid carting duty, which includes sitting in an hour + of traffic...in the hot hot summer. Which is surely going to have me and the kid high as a kite on gas fumes 3 days a week. So previously it was an annoyance that crept up very rarely, now it's a big problem.

So yea lazy in the sense that when it crept up for a day or two I didn't get to it. Then it came back years later.

Explain it better, ya::Bum::::Clown::

;)

Here is a thought - clean the valve out and report back your findings.

Or just keep posting every few years it is your choice! ::Grouphug

I want my flywheel back.
::Banana::

Jiggerachi, I thought everyone knew that if POS gives you money for anything, he thinks he owns you ;)

Didn't even give me anything for it...

Took off work early, just yanked the valve in question. A little gas dripped out of it.

Finally got the rusty screws out of the rusty plates. I hit them with PB Blaster and then had to dremel slots in them to use a flat head screwdriver. Halfway in I realized I was lucky I didn't start a fire(heat+sparks+ petroleum product) Pulled the valve and it seemed to be working normally, both one way valves were still only flowing one way(although the one with the arrow was flowing opposite the arrow :scratch:) I hosed it out with seafoam anyway.

Assembled everything and moved to the charcoal can. Pulled it and BINGO the hose connecting under the can was split wide open. I guess that's probably the problem.

Anyone who has pulled the can have the hoses still laying around? I might be able to get it from the dealer, I didn't see it on Rosenthol's site.

Is it regular fuel line hose? Cheap at your local Vatozone.

I'm not sure. It's a pre formed piece with an elbow. Fuel line might work, but the OEM piece will probably be better. I might grab a cheap hose and see if it kinks or not.

This is what I have left of my charcoal can stuff:

http://www.guapozx.com/users/dogpile/charcan.jpg


If any of it looks like what you need, it's all in good shape - no tears or splits, but not as pliable as brand new rubber. It's all from a 1990, but only has about 40k miles on it.

Looks a little different, but that hose at the bottom looks the same (I think. Should have grabbed a pic). Either way the hose with the elbow i'm sure I can make it fit better than generic hose that would possibly kink.

Wait...which is the top, the side with the gray metal lip? On the 94+ the two smaller hoses are at the top and the nipple for the drain hose is straight down, thus the elbow. Looks like the diameters are close to the same. Might work.

Actually let me run by a vatozone tonight and see if I can get something to work. I'll let you know if I can't.

The top is the end with the two hoses (silver and the black). The single bottom hose is just a rubber hose, nothing special. The one on this 1.6 can could very easily be a generic fuel-safe hose, I would imagine the 1.8 can would be the same (like I said, I've only pulled them so I never took note of anything like that). I'm sure you could gently tweak the bottom nipple a bit to straighten a generic hose too, but of course try at your own risk.

I think the can is plastic on the 1.8, including the nipples. I ran out of time and was in a hurry by that point yesterday so I didn't take as close of a look as I should have though. I might be able to make a longer hose maybe hang down and make the bend. I'll get a generic hose and play with it more tonight.

BTW nice job on the title, whoever changed it, haha.

Got some gas line from O'Reiley's that I was able to massage in place without crimping. Drove it home and left it running for a half hour. Son of a... gas smell. Nothing's changed. Now i'm stumped...

When I get another free day, maybe sunday i'm going to pull all the lines attaching to the charcoal can and inspect them, but not sure i'll come up with anything.

Two fill ups without topping off, still have the problem.

I read that the hose that was originally split is just an overflow hose that runs under the car and vents to the atmosphere. That would explain why I still smell gas after replacing it, just slightly less. As an experiment when I got home today I pulled the can, pulled the drain hose, hit the ac and waited for the stank. Sure enough 10 mins with the AC on was enough and i was able to confirm 100% that the gas smell is coming out of the pressure relief hose at the bottom of the can. I could hold my thumb over it and it would slowly build pressure and pssssshhhh when I let it go.

Opened the gas cap and lots of pressure was released. I seem to have some sort of pressure buildup in the tank, instead of a leaky injector or something on the fuel rail ($$$).


I'm almost positive now that my spuddering idle problem is related. I park with gas smell, then crank an hour later the engine will consistently spudder / miss for about 30 secs. Seems like the excess pressure being vented leaves a negative pressure in the tank after it cools. Next time this happens i'm going to open the gas cap and i'm betting it will straighten out.

So, what could cause a vapor pressure buildup, maybe this is normal and Miatas just aren't good at filtering it...any ideas? I'm going to go pick up a new gas cap just for good measure.