Home page

Forum: C3 Fuel, Emission Control, and Exhaust Systems

Topic: Gas smell with full tank

Gas smell with full tank (1/15)
 11/13/03 2:04am
ricknhis69
Former Member

Send Private Message

Joined: 3/9/2003
Posts: 281

I know that there have been discussions on this topic before but they have mainly been with the later C3's. My '69 always smells like gas when the tank is full after a drive. The smell goes away until I drive the car again and then its back. This continues until I'm below 3/4 of a tank.

I've been over every inch of the fuel system from the carb all they way to the right rear tire and I've never found a leak. The gas tank is not leaking at the seam and I have not been able to find a substanial area of wetness on the outside of the tank.

Does a '69 have a charcoal cannister? Is there a gasket between the filler neck and the tank body? (this is my best guess as to where some seepage might be occuring) I haven't seen any evidence as to leaking fuel lines. Does anyone else have any suggestions? |headscratch|

______________

'69 350/350 conv.

Our Sponsors help support C3VR
Gas smell with full tank (2/15)
 11/13/03 9:04am
markdtn
Former Member

Send Private Message

Joined: 6/16/2003
Posts: 252

The 69 has a vented cap and no vapor canister. Mine smells a little with a very full tank, but not much after that. I have a new cap-less than 1000 miles. I would make sure the cap was sealing well to start with.
Gas smell with full tank (3/15)
 11/13/03 7:59pm
Mr69Vett
Former Member

Send Private Message

DE PERE, WI - USA

Vette(s):
1969 350, 4-spd, 3.53 gear, side exhaust, custom mix yellow PPG base/clear Brilliant Yellow


Joined: 12/9/2001
Posts: 231

Same here, gas smell when the tank is full. My cap is also in question, just haven't got around to getting a replacement. One other note is if the cap is leaking fuel it is going around the fill neck onto the collar and then running down the overfill tube. I guess the nest time you fill up, you could take a ride, when you stop, make a point to check up by the cap, I have seen my wet so I know its sloshing in the tank coming out the top and running down. And I Still wonder why I can't get more than 10 MPG |biggrin| |laugh| , couldn't be that way I drive also? |headscratch| , ot a chance |smokin|

Dave
Mr69vett

______________
|IMG|https://www.c3vr.com/member_uploads/201_300/274/yellowvette.art|/IMG| |IMG|HTTP://www.c3vr.com/member_uploads/201_300/274/yj.jpg|/IMG||IMG|https://www.c3vr.com/member_uploads/201_300/274/C3vr2002A.jpg|/IMG|
Gas smell with full tank (4/15)
 11/19/03 2:31am
ricknhis69
Former Member

Send Private Message

Joined: 3/9/2003
Posts: 281

I have seen wetness on the bottom of the cap but I have never seen any around the collar where the overflow when filling is designed to drain off. The cap does appear to be an original so I think I'm going to try replacing it.

Does anyone know if the filler neck has a gasket between it and the tank?

|headscratch|

______________

'69 350/350 conv.

Gas smell with full tank (5/15)
 11/20/03 12:43am
debrown
Standard Member
Send Private Message

Mammoth Lakes, CA - USA

Vette(s):
1971 LS5 Convertible with M/T, A/C,Brandshatch Green, Saddle Leather interior, numbers match


Joined: 11/15/2003
Posts: 36

I just recently joined this group, and I don't know if you still have the problem or not,but I had a gas smell when I had a full tank and/or turned corners that caused the gas to slosh in the tank. I discovered gas had leaked out a separator assembly, which is a small black plastic box containing a check valve and mounted on the driver's side of the gas tank. It's connected to the return line from the fuel pump and to the fuel tank by rubber hoses.

In my case, the separator box was leaking at a joint in the box, leaking gas down on the exhaust muffler (and could have been a major problem). So I removed it, after first removing the spare tire container, took it apart at its joint, cleaned it and reglued it with a gasoline resistant glue.

It hasn't leaked since.
Gas smell with full tank (6/15)
 11/20/03 1:38am
ricknhis69
Former Member

Send Private Message

Joined: 3/9/2003
Posts: 281

Does anyone know if a '69 has this?

|headscratch|

______________

'69 350/350 conv.

Gas smell with full tank (7/15)
 11/20/03 10:10pm
Mr69Vett
Former Member

Send Private Message

DE PERE, WI - USA

Vette(s):
1969 350, 4-spd, 3.53 gear, side exhaust, custom mix yellow PPG base/clear Brilliant Yellow


Joined: 12/9/2001
Posts: 231

Rick, I just looked thru my assembly manual and yes there is a gasket between the filler and the neck. I have a part # 0f 3826417, not sure if that will be a good GM number though. Looks like there are 8 bolts from tank to filler neck. Good Luck.

Dave
Mr69vett |smokin|

______________
|IMG|https://www.c3vr.com/member_uploads/201_300/274/yellowvette.art|/IMG| |IMG|HTTP://www.c3vr.com/member_uploads/201_300/274/yj.jpg|/IMG||IMG|https://www.c3vr.com/member_uploads/201_300/274/C3vr2002A.jpg|/IMG|
Gas smell with full tank (8/15)
 11/29/03 4:42pm
Paul Borowski
Former Member

Send Private Message

Massillon, OH - USA

Vette(s):
1968 International Blue conv 1968 Silverstone Silver coupe 1974 Orange coupe 1975 Silver coupe 1980 Yellow coupe


Joined: 1/20/2003
Posts: 6

rick, only Corvettes that had the "charcol canister" had this 'black plastic seperator". They vented to a 1/4" steel line that ran along the driver's side frame rail to the charcol canister. The car's that also had these charcol canisters had "SEALED" gas caps(late '71/'72 |headscratch|). You may have such a small leak(like happened with my '75)that you'll only smell the vapors and NOT see liquid. Could be as simple as a loose or rusted fuel line clamp, to a very, very small age crack in one of your rubber fuel lines, either supply(the larger one) OR your return(smaller line).
Gas smell with full tank (9/15)
 12/11/03 1:13am
ricknhis69
Former Member

Send Private Message

Joined: 3/9/2003
Posts: 281

Paul, I agree that it only takes a small leak to create a lot of fumes, but, why does it only happen over 3/4 of a tank? I would think that if hoses where the issue I would have an odor regardless of tank level.

Once the level in the tank drops, there is no smell at all.

|headscratch|

______________

'69 350/350 conv.

Gas smell with full tank (10/15)
 3/17/06 1:09pm
Adam WartellLifetime Member
Lifetime Member
C3VR Founder
Send Private Message

Eagleville, PA - USA

Vette(s):
Used to own a 1979 Corvette now owned by JB79


Joined: 11/1/2001
Posts: 15461

So, I just did a search on "Gas Smell" here and found this thread.

My 79 does the same thing, and it is in the shop right now for that very reason.  The mechanic did in fact determine that the tanks leaks at the top when full.  I still have to speak with him directly, in about an hour.  I will reply again when I get more detail. 

One of the things I want him to be careful about, is looking for a build sheet!



______________

-Adam Wartell
NCM Lifetime Member #1222
Founder: C3 Vette Registry 
C4 Vette Registry, C6 Vette Registry

My first Vette, now owned by JB79:

Gas smell with full tank (11/15)
 3/17/06 2:45pm
warbird
Former Member

Send Private Message

Roseland, NJ - USA

Vette(s):
1974, 454 with 4 on the floor, matching numbers.


Joined: 12/4/2003
Posts: 966

I had the same problem on my 74. I replaced the fuel cap which was bad, but the main cause was the over flow hose which was cracked at the top by the fill spout. It never leaked enough fuel to leave any sign of a leak, but it did emit a strong gas smell. Fixed the hose, no more gas smell,  
Gas smell with full tank (12/15)
 3/17/06 11:01pm
Adams' AppleLifetime Member
Lifetime Member
Moderator
Send Private Message

Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 19718

The filler neck on the later cars(77-82) were sealed by the "Bladder". It formed the seal for the neck, as well as being the bag for the fuel tank. If it is leaking at the filler neck/tank junction, chances are the bladder itself is bad. The good news is, you can completely remove the bladder, and seal the neck with a cork gasket, like the older tanks were.

This is a pretty old thread!! That "search" function is purty neat, eh Adam??

______________
Joel Adams
C3VR Lifetime Member #56    

My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
Gas smell with full tank (13/15)
 3/18/06 6:38am
dwrightGold Member
Gold Member
Moderator
Send Private Message

Victor, NY - USA

Vette(s):
2004 Commemorative Edition Coupe, Auto w/HUD. 13K miles in 2015. Sold 1982 Red Coupe


Joined: 7/12/2004
Posts: 6796

If you are going to replace the cap, consider a locking cap. With the price of gas always going up, I wanted to make it more difficult for the gas robbers.

______________

Save the Wave!
Support the National Corvette Museum   
Gas smell with full tank (14/15)
 3/24/06 11:14am
gs77vet
Former Member

Send Private Message

Joined: 3/19/2005
Posts: 385

be sure you do not over fill, if you do you might get some splash back around your gas cap. that makes a nasty gas smell.gene gs77vet38800.3441550926
Re: Gas smell with full tank (15/15)
 12/26/17 10:47pm
Pberns
Former Member

Send Private Message

Camano Island, WA - USA

Vette(s):
1969 427 Coupe


Joined: 6/9/2017
Posts: 2

My sending unit gasket was leaking changed it out and the smell went away.

______________
Our Sponsors help support C3VR