Ok, I have some sort of "minor" gas fume problem with my 1978 Pace. Here is the history...

Up until last year, everything seemed fine.

When I stored it in winter 2002 with a full tank of gas, a leak developed in the rear end of the car. I thought it might have been a leaking rear differential, because it was black on the garage floor and was coming from near the rear hub. (It was a pretty steady leak...Not a stream, but a couple drips a day...Definitely noticeable.) It turns out that it was not the rear differential leaking, but instead it was fuel dripping (and the blackness was just dirt it was “cleaning” off the differential on the way to the ground.).

My Corvette mechanics "initial guess", before seeing the car, was leaky fuel lines from the tank to the front of the car (right rear quarter panel area) dripping down the frame and onto the ground near the rear differential. (Apparently this is common with C3s?!?) It turned out that the fuel lines were not leaking, the frame was dry on the right side. He said something about a 'pressure backup' in the system (I can't remember his reasoning...). So, he vented the gas cap, and the leak did in fact stop.

Now, occasionally I will have a fuel smell in the garage, with no drips. At first I thought it might have been gas in the carburetor, but now I don't believe that is it. Some days I will smell fuel and other days I won't, so it is not always leaking. It does not seem to be related to how recently the car was driven. The smell will some times appear even two weeks after driving the car. It does not seem to be a factor of how full the fuel tank is..

Ideas? :confused:

 

I think your mechanic was right on! now I think what your smelling is just the tank venting. And the smell probably changes with weather, you know if you leave a plastic gas can unvented in the sun-and then vent it or open the can you can hear it vent or actually see the plastic structure change from swollen to smaller. I know it probably buggs you, but I wouldn't loose sleep over it.

Good luck

 

I could believe that it is fumes coming out the vented cap..

The think that baffles me is the leaking problem, other than some odor, went away with a vented gas cap. (Even though a vented gas cap should be unnecessary, in a 'closed' system.)

I did find this in my service manual..
(Ignore me if this is totally off the wall...Just talking out loud here.....)

Evaporative Control System (ECS) / vapor canister. "...During periods of inoperation, an activated charcoal canister located in the emission line stores any vapor generated for comsumption during the next period of operation."
Since we are talking about times when the car is off, and just "out of the blue" that this odor occurs.. I assume it could imply the problem is with the vapor canister part of the system?

"Maintence requirement is only that the oiled fiberglass filter assembly in the bottom of the cainster be repalced every 30K miles"
Could a bad filter in the canester to be letting vapors escape? Seems unlikely to me... Although I am quite certian that filter has not been replaced in a LONG time...


[Modified by Sting1978, 2:51 PM 12/10/2003]

 

Ok, I think I have a new tidbit of info on this...

I believe the vapor cannister has been removed, and is not capped. http://forums.corvetteforum.com/zerothread?id=708600

Would this cause problems? I have read previous posts, which indicate if the vapor canister is removed that the line should be capped (and a vented gas cap is needed). Previously my gas cap was not vented, and I was having a leak which I believe was caused by a pressure problem. Wouldn't the open end where the vapor cannister effectively vent the system?

Ideas?

 

If the vapor cannister was dis-connected and not capped it certainly will vent the tank. You could have a small enough leak where it's not dripping, but evaporating as fast as it leaks. Paul Borowski just started a thread on this, he found a leak where the fuel lines pass by the transmission cross member. Not enough to drip, but enough where moisture would show, and certainly an odor of gas.

 

Check the fuel pump weep hole. I had the same problem and it turned out to be the pump.