47-55.1 Gas smell

[72Mountaineer]

I have a rear fuel tank in my 53, non-vented cap but a vent tube with a rearend vent in the hose end. Getting a smell in my small garage, not bad but very noticeable. How is everybody who has this setup blocking the fumes?

[joedoh]

everything without a charcoal canister will have a gas smell. if your tank has a vent output (sounds like it does) try putting a charcoal canister from a late 80s s10 or fullsize on it. make sure it is higher than the tank so when you accidentally overfill the tank it doesnt start a siphon.

[dsraven]

the other thing it may be is fuel evaproating from the carb after a hot engine is shut off. open the hood about an hour of sitting after the engine has done a normal drive and is up to operating temp. if you smell gas under the hood, an there are no leaks, then a fibre spacer under the carb may help to keep the carb from absorbing a bunch of engine heat.
otherwise check for any damp spots along the whole fuel line system from front to rear. sometimes a realy small seap can make a big smell, and it's a big fire hazard inside your garage. if it's attached to the house, even worse hazard.
if you can't find a source, and joedoh's answer doesn't fix it (you may wanna do that one anyway), what I have done in the past is put a small pressure in the tank, through the vent line, and see if it holds. if it doesn't hold then, again, start looking along the fuel lines, under tank straps, around the sending unit seal, the filler hose connections, etc etc. is your truck carbed, injected? is the tank mounted with some sort of rubber or shock absorbing material between the tank and the mounts? sometimes a tank can get a pin hole from how it was mounted, especially some of the newer really thin tanks.

[mr48chev]

Joedoe said the same thing almost word for word that I was thinking. Mount a charcoal canister up front where it is hidden and high enough and run a line to it.

[72Mountaineer]

Those who have suggested a charcoal canister, the ones I have encountered must have a line going to the carb to burn the vapors. Is there one that doesn't? As far as I know, thats not the way they operate. The smell isn't huge, just annoying enough that I can't park the truck in the garage under the house. I've checked for leaks, none, and the smell is coming from the tank, not the carb.

[unclebrad]

Mine had vapors from the tank and, after tearing my hair out for weeks, I solved the problem by replacing the fuel level sender gasket. The old one was rubber or neoprene or something like that. I went to cork.

[joedoh]

the older ones go to the intake, yes, the newer ones use a vent valve that is triggered by the ignition, no line to the intake. you could get a pulse relay from a place that sells alarms and set it to open the valve for 3-30 seconds when you turn the ignition on.

charcoal canisters are meant to handle fumes from the tank, not the carb. i remember this as a kid, walking around the thorofare parking lot, in the summer all you smelled was gas from the car tanks vented caps. charcoal canisters are not really necessary (except for california I guess) except to keep from smelling gas in your garage.

[Socal_Dad]

On a Vette I had, I changed the gas tank and had a heck of a time chasing a gas smell. It turned out to be gas wicking up the threads of the bolts for the sending unit. I used Honda Bond on the threads and both sides of the gasket and the problem was solved. You can pressurize the system with a bicycle pump to keep the pressure to a couple of PSI and spray soapy water to find where you have the seepage.

[leegreen]

Joedoh, I've never had to mess with a charcoal canister. For the ones you are talking about, how do they handle expansion like when the truck sits in the sun?
Where have you mounted them on an AD, inside fenders?

I've avoided filling my main tank while the truck is still a project living in the garage. I have a small non vented tank zip tied to the frame under rad I run it off for now, just have to remember to loosen the cap before firing up.

[dsraven]

I have chased gas smells on lots ofvehicles over the years. a common one is the hose connections on the filler tubes, a sending unit gasket (not often the screws, but those too occasionally), a rusty spot on the back side of a frame mounted fuel line, a fuel pump leaking out the evnt hole due to a cracked diaphragm in the pump, fuel seaping out of the carb float bowl and out the throttle shafts due to a poor inlet valve needle and seat (after vehicle is just shut off, fuel leaks until pressure in the line is bled off), a leaking inline fuel filter housing, a fuel tank pin hole under the tank mounting straps, a leaking pinch weld on the tank where the upper and lower halves come together, and several other dumb ones. first looking for a damp spot, these usually are spots hat have collected some dust on the damp spot if the vehicle has been driven much. if you have access to dyed fuel it can help as the leak will show up as a coloured spot if the has dried up, which sometimes happens if the leak is near the top of the tank. check all along every line starting from the filler neck at the cap and then to the tank, top and bottom, sending unit and gasket or O ring seal, straps, pinch weld etc, then move along to the fuel delivery lines, filters, fuel pump-if not in tank, and up to the carb or injectors.remember to check the return lines and vent lines as well. on vent lines I like to use a long hose that goes up higher than the tank, diff, trans or whatever I am venting, and then makes a u turn and comes back down a little ( like an inch) before terminating. this keeps any water splash from dropping in. never lower than the top of the source or a siphon can get started. I use a diff vent on the end of the hose to keep debris out. a charcoal cannister is a great idea. I have had to use a slight pressure in the tank sometimes in order to force a leak to show up where it may not normally be visible. slight pressure, like a couple psi and be carefull when you release the pressure as it can bring fuel along with the air when the release is too fast. a full tank of fuel is sometimes a good idea to try after first trying it on less fuel in the tank but not finding anything. dont forget to check down the throat of the carb and around the throttle shafts.

[joedoh]

Originally Posted by leegreen

Joedoh, I've never had to mess with a charcoal canister. For the ones you are talking about, how do they handle expansion like when the truck sits in the sun?
Where have you mounted them on an AD, inside fenders?

I've avoided filling my main tank while the truck is still a project living in the garage. I have a small non vented tank zip tied to the frame under rad I run it off for now, just have to remember to loosen the cap before firing up.

all the s10 swaps i have done have kept their charcoal canisters, so if they were under the hood or under the bed thats where they stay. the sealed burp systems from ~2001 didnt have a pressure sensor so i would guess they just held pressure, there is a shuttle valve in the tank that closes off the filler neck when fuel isnt flowing in so they dont even need a vented cap.