Now with winter upon us here in Upstate NY [thank God we don't have the 5 -6 ft. of snow they have in Oswego, NY!] I've been keeping the Bonnie inside the garage & have noticed that anytime I have more than a 1/2 tank full I'm smelling some serious fumes...
I haven't been able to spot any puddles that might help me locate the source yet, but then again, it'* not like the garage floor is dry at all this time of year
Any suggestions as to what I should be checking/looking for that may help me narrow it down? :?

I went through that a few times for different reasons

Has the tank been dropped recently (fuel pump replaced, etc?) If so, then its possible that the seal on the top of the tank failed or was improperly seated.

If not, look at the tank for 'wet (with fuel) spots'.. The salt from the roads tends to eat away at the tanks and related lines, causing rust through and ultimately leaks.

I know both of these to be true on other GM lines, although someone else with more H-body experience may be able to give you specifics.

No, I haven't dropped the tank to do any work on it...
And I'll have to wait until this weekend to jack her up to look for wet spots on the actual tank.
I don't think this could be an Evap Cannister or any of the vacuem lines attached to it, could it? :?
Because if it was, then I imagine I'd smell fumes all the time, not just when there is more than 1/2 tank...and the same logic would point away from gas lines, correct? :?

Yeah, the above half a tank thing is what makes me lean more towards the tank, although I would keep all possibilities open, as I have seen cars do weird things. Also look at the fuel filler assembly, I have seen those rust out and leak often as well. check for leaks at all the visible fittings under the car.

Isn't the things that salt does to our cars great?

Let'* say that this weekend I am able to find 'wet spot[*]' on the tank itself: if they appear to be minor holes, is there any product out there that could be used to patch with?....
Or am I forced to get another tank :(

gm makes the tank in most cars - not sure about the boony - in two piecies and then where the combine is a lip. the lip is turned upward (stupid move) as it collects dirt/road salt/etc. More than likely you have pinholes around the seam. (the 1/2 tank area) Replacement has always been the best option because I personally have not found anything that will seal the tank and last. There are some things you pour in the tank but the tank has to be removed anyway.

FYI with this Lip the sending unit lines are about 1/4 inch away from the tank allowing the dirt/etc to corrode the metal lines. Again not sure on the bonny but most sending units are metal lines and then plastic.

So in short.. look for another tank if this is actually leaking and price the sending unit just in case.

Windshield time is right about the lip- that (or ocassionally the top of the tank) is where they usually first start leaking.

I have heard of people ahving tanks repaired, but in this case, your best option- especially if you plan to keep the car, would be to replace the tank with an aftermarket unit. the patching compounds usually do not last more than a month or so, even when done properly. IMO, not something that i'd risk doing.

The tanks generally run around 100$, and are not too horrible to replace. You will probably have to replace the tank straps as well, as they tend to corrode out.

The sending unit may be OK, it'* best to make that determination once the tank is out of the car, and you can see the lines in their entirity. I am pretty sure the older bonnevilles were completely metal, especially if they are similar to older LeSabres, but i am unsure of the 92-up models.

Thanx for the input guys...Although I haven't jacked her up & looked yet, I have done a little legwork & I found I could get a replacement [new] tank, a new sending unit & new [stock] fuel pump for about $300.. so I wonder if I'm just not better off getting those [along with new straps: I doubt I could re-use the old ones anyways] to be done with it... :?