Gas Smell FYI

[DC3]

Ever since I bought my '73 a couple of years ago, I've been chasing a garage gas smell.

The carburetor had issues when I bought the car so I assumed it was the problem. After a carb rebuild and dyno tune, the situation improved somewhat but the gas smell was still present.

I discovered the previous owner had eliminated the vapor canister and the vent line from the tank was open. Tracked down a new vapor canister and finally got it installed. That also helped tone down the smell but it did not completely eliminate it. As it always had been, the smell was much worse when the tank was full.

Well, a few weeks ago, my starter was acting up and I decided to replace it. I jacked up the right front of the car and began removing the old starter. Part way through that task, the smell of gas in the garage became overwhelming. Stopped what I was doing and took a walk around the car and discovered gas dripping off the driver's side muffler. Not good. It was early in the morning and I had not been driving the car so at least nothing was hot. I had gassed up the day before and so the tank was full.

The plastic gas tank vent valve/separator had failed. More than once it turned out. After removing the part I discovered one of the nipples had been epoxied back on after a prior failure and the epoxy had failed. I also discovered the valve had been remounted upside down.

After replacing the valve, my garage gas smell is now history. :yahoo:

Replacing that valve is an interesting challenge. It can be done without removing anything else but you have to work blind and with only one hand. Guys with large mitts may not make it. I cussed. A lot.

So, my advice to anyone facing the garage gas smell is to completely inspect the system from the gas cap to the carb and don't stop if you find a problem because you could have more than one issue.

DC

 

[Frankenvette]

Ever since I bought my '73 a couple of years ago, I've been chasing a garage gas smell.

The carburetor had issues when I bought the car so I assumed it was the problem. After a carb rebuild and dyno tune, the situation improved somewhat but the gas smell was still present.

I discovered the previous owner had eliminated the vapor canister and the vent line from the tank was open. Tracked down a new vapor canister and finally got it installed. That also helped tone down the smell but it did not completely eliminate it. As it always had been, the smell was much worse when the tank was full.

Well, a few weeks ago, my starter was acting up and I decided to replace it. I jacked up the right front of the car and began removing the old starter. Part way through that task, the smell of gas in the garage became overwhelming. Stopped what I was doing and took a walk around the car and discovered gas dripping off the driver's side muffler. Not good. It was early in the morning and I had not been driving the car so at least nothing was hot. I had gassed up the day before and so the tank was full.

The plastic gas tank vent valve/separator had failed. More than once it turned out. After removing the part I discovered one of the nipples had been epoxied back on after a prior failure and the epoxy had failed. I also discovered the valve had been remounted upside down.

After replacing the valve, my garage gas smell is now history. :yahoo:

Replacing that valve is an interesting challenge. It can be done without removing anything else but you have to work blind and with only one hand. Guys with large mitts may not make it. I cussed. A lot.

So, my advice to anyone facing the garage gas smell is to completely inspect the system from the gas cap to the carb and don't stop if you find a problem because you could have more than one issue.

DC

Interesting post. I too have been smelling gas fumes for years, so just last week I found someone with an vapor canister and bracket. Mailing him the check this week. Others have also suggested that there could be more than one source for the smell. I rebuilt my rear suspension a few years back but never noticed any gas leaks nor even a stong odor, so I'm hoping mine is simply the vapor line. Then again I'm never that lucky.

Jim

 

[mrvette]

Previous owner from over 15 years ago had installed a 'GM replacement' tank, with GM parts sticker on it, so my '72' tank should have been pretty close to the OEM from St. Louis.....

I have fought this smell crap a LOT since here in Florida...because garage faces directly west with no shade....sun heats ass of car, tank right under there, and so the smell by 4+pm.....especially when full.....

have noticed pressure build up in the tank also....released when the stockish cap was pulled....it was + pressure, not a vacuum.....

so I noticed how the stock float ball separator worked, and noted that the front valve on the canister no longer worked, stuck open....not an issue, since it is routed through the canister into the engine per stock, just always open....BUT if the float ball in the separator is held in the up position by fuel level, OR you drive a goodly distance after a fill up, and + pressure was in the tank, that pressure will keep that ball UP and closing the evap line....

another point I have NO CLUE what it was/why it was there was some fitting on top of the tank to the driver's side forward of the filler cap, pull that useless rubber drain boot off and you can see it...was there in mine, anyway...some kind of 'tit' looking fitting, welded on the tank, caught it spitting gasoline....dried it off, carb cleanered it down....blasted it dry, and epoxy all over it.....no more leaks/vapors.....

but still under the right conditions, full tank/pressure holding the silly vent ball closed, I got + pressure in the tank....I don't like that one damn bit....since I have FI, the return line is of course much hotter gasoline that what's in the tank, adding to the problem....

the way I bought the car, that filler cap was a non vented type....due to other issues, I have a locked cap on there now....it's vented....

no more issues with the fuel tank/valves/canisters/whatever.....

had this car 2 years in Maryland, and so a north facing garage door, never an issue.....850 miles south facing WEST, and yuppers, out come all the gremlins......

13 years of observations on that thing, try this/that....finally found it...no more gas fumes that my wife is SUPER sensitive to...gives the kid a headache....to me, it just stinks a little....:rofl::thumbs:

 

[Stuart73]

I have 73 with same problem. If tank is full gas pours out of top of tank, driver side. Please tell me how to remove the vent valve without pulling the tank!

 

[mrvette]

I have 73 with same problem. If tank is full gas pours out of top of tank, driver side. Please tell me how to remove the vent valve without pulling the tank![/QUOTE

Welcome to the motley crew of the Flying Dutchmen....

Those black plastic float/separator valves are way up top mounted to the tank flanges for it, with two 5/16 capped hex screws, the hoses are 3/8 to the bottom of the valve from the top of the tank the hose to the front charcoal canister under the driver's fender on the frame behind the tire...is 1/4 or 5/16 they all held with typical clamps, you can see the valve and hoses with a strong flashlight, and reach up there fairly easy with the car on the ground....

those plastic valves will split open along the glue line and drain gas super easy...

:crap:

 

[Stuart73]

Gas Smell

Thank you for the information. If it ever cools down enough, I'll crawl under and take a look. I sure sounds better than pulling the tank.:thumbs:

 

[mrvette]

Thank you for the information. If it ever cools down enough, I'll crawl under and take a look. I sure sounds better than pulling the tank.:thumbs:

:lol::lol: by the time you do the 'while I'm at it's'....yeh by about 6 hours....

do check for tank rust though...one of them LED lights into the tank and a good peak should see enough....MY tank was new from P/Owner....

 

[Stuart73]

The tank appears to be new - also from previous owner. It looks clean inside.

 

[Stuart73]

Gas Smell Fixed

:thankyou: You guys are awesome. I made the repairs, with your information, in less than 2 hours. It is DEFINITELY a challenge to your dexterity to do this project. It's all with one hand and much of it is by touch (no can see). But both of my gas lines to the valve were rotted and the valve was cracked as was mentioned. A suggestion for anyone else, take the radio ground loose at the frame to give you a little more room. Also, attach the new gas lines to the valve before re-installing, and put the clamps on the open end of each hose so you just have to slip them down to complete the job. Thanks again!!!!!!

 

[DC3]

Also, attach the new gas lines to the valve before re-installing, and put the clamps on the open end of each hose so you just have to slip them down to complete the job.

That's the way I did it. The previous owner of my '73 had used some non-standard slotted screws that were a pain to get out by feel but I managed to get it done with a short handled screw driver. I happened to have a couple of socket head cap screws handy that were the correct size which ended up making the installation a bit easier. The socket heads were very easy to grab and turn with my fingers so I taped them to the valve before starting the install. I put duct tape on the back side of the hole in the valve mounting tab, then poked a small hole in the tape and pushed the bolt through. It held perfect. Then all I had to do was get it lined up and turn the screws with my fingers to get them started. Finished up with a small allen head ratchet I happened to have.

I had a hard time finding a new valve as they were back ordered everywhere until the end of September but I finally found some in stock at Corvette Pacifica. Because the valves have a tendency to crack at the seams, I sealed the new one before installation. Hopefully I bought myself some more time before I have to do this again.

DC