Thread: Gasoline odor

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I need some ideas - and I also asked this on the other forum I follow. Unfortunately the ideas didn't pan out so I need some other fine minds thinking about this.

My '31 has a rear mounted gas tank - a Tanks, Inc '32 tank. It has their standard roll over valve which is also the tank vent as well as an unvented fill cap. The fumes coming out of the vent hose are b-a-a-a-d and to the point that there is even some liquid. Overnight with the garage doors closed it's unbearable until it airs out. One suggestion was to use an early '70's Chevy p/u vapor canister. Not a bad idea but they are fairly expensive (new ~$90) and in my area junk yards have processed vehicles that are that old into scrap to be shipped to Japan and made into econoboxes or they are blobs of rust in a field. Also it would require a couple of lines - a vacuum line to operate the canister and a line to the PCV or vacuum connection in the intake manifold - in other words, a sloppy mess of hoses. Do I need to vent the cap? I wouldn't think so. But....

I'm in the process of trying something I made up using an activated charcoal filter (a Brita water filter). So far, the results haven't been successful, but I forgot to water soak the filter to activate it to work. It's been soaked and on the vent now, but my guess - it ain't gonna do it!!

With that said, others must have had excessive gas fumes from their gas tank vents and on street rods. How were those fumes handled? Why this car when others didn't have that problem? And before you ask, there is only about a half tank of gas.

HELP

i think your roll over valve maybe to close to the tank if pushing fuel out the tank .could loose the roll over valve and make up a loop ?

Strange that you never mentioned or noticed the fumes before.!.! Was this the same tank in the car all this time? I used a tanks system, tank & roll over valve and have never noticed fumes around the car! Are you running a return line back to the tank?

OK guys, this is the vent/roll over valve that's in the tank top itself:



It's one of the two types that Tanks, Inc supply based on what vehicle the tank is for - the other is one that fits in a fill door or in a fender well and at the end of the vent line. There has always been a little bit of gas odor, but since I put more then a gallon or two in the tank(probably has 6-8 gallons now (14 gallon capacity), it's gotten much worse. Pat, I actually added about a 5' length of tubing, ran it through the frame to the back side of the rear fender and coiled it up behind a fender brace - no help. The next morning, same thing.

Mike, with a Performer carb and Carter mechanical 5-6# output fuel pump, I don't need a return line

This is an early version of the tank plumbing before I went to a 3/8" hard SS gas line. The vent/roll over valve is the brass fitting in the middle. The tubing comes from that valve to a point about an inch or so below the bottom of the tank:

Dave,
Evolvo was just a bit ahead of me hitting "submit", and I went back to look at your post again so I'll state that I agree with his analysis. The picture of the tank helps, as I was having a hard time envisioning your layout based on my trunk mounted Tanks, Inc tank. Your vent/rollover valve ball rolls freely in the tube, I assume? With that step down in the front of your tank the bleedback hole on the rollover valve tube could be submerged if you top off your tank, couldn't it? Doesn't explain liquid coming out with only 1/2 tank, but I think the answer is to run your overflow tube up from that fitting as far as you can before looping it back down as Evolvo said. Not sure that you couldn't just terminate it up high, like at floor level above your differential, but a little down turn is probably best.

looks like its in the lower part of the tank wrong place should be at the higher point on the tank or up higher the tank . i think it is siphoning try a riser on it or plug it and just run a vented cap or vent the filler neck

Evolvo What you are saying about that little pumping action is exactly what I believe is happening with the non vented gas cap. Yes, I could vent the cap by drilling a small hole, but then I run into two problems - possible slosh on my new $$ paint and a second fume exit.

Now, the hard part - room for much modification above the tank - not much. I have a standard 'A' trunk with a high sill that might allow a few inches for a loop, but probably not to the height of the tires. And since I actually have an access hatch for the sending unit and have to open it to fix the ground will give it a shot. If it works, then I'll do a more permanent mod, but with that expansion and contraction of the vapors, am not convinced. YET

Whatever the fume outcome - I am still enjoying driving the car

I like Pat's approach. If you have room immediately above you could make up a pipe riser to get the bottom of that valve at or above the top of the tank. Still does everything it is supposed to do.

Good idea, Pat!!

Pat and Roger, you snuck in there while I was doing my two finger typing.

I'll not only try the vent line higher, I'll add a riser of sorts. I do want to keep that valve in there. Off to Home Depot in the morning as I need more tubing and some fittings. A pipe nipple and a couple of bushings and I'll take that valve right out of the tank. If I don't get ahead of myself, photos to follow

(It's a b@#$h to get in there)

Easy fix. Like others have already stated you need to build some elevation into the vent hose to prevent the fumes. Think of the way a sink trap works (in reverse) with standing water in the J-Tube to prevent the sewer gas smell from backing up into your house.

Just connect the vent hose to a piece of 5/16" steel flared tubing. Run the tubing up through the trunk floor or behind the rear seat. Run it all the way up to the highest point and bend a 180 (u-turn) in it, and then back down through the floor again. I then took a 1/8" NPT Ford type carb fuel filter and screwed it into the boxed frame and a short piece of hose connecting it to the new vent tube. The gas tank is vented to atmosphere through the frame "outside of the body" but running the tube through the body allows the height needed to prevent the fumes. Just make sure you size the vent tubing based on your estimated fuel consumption. It works!

2 finger typing i'm impressed, i'm still using 1

I've had a similair problem and solved it by takeing the breather pipe up to just below the height of the tulip panel and then back down again through the floor.

Originally Posted by IC2

Pat and Roger, you snuck in there while I was doing my two finger typing.

I'll not only try the vent line higher, I'll add a riser of sorts. I do want to keep that valve in there. Off to Home Depot in the morning as I need more tubing and some fittings. A pipe nipple and a couple of bushings and I'll take that valve right out of the tank. If I don't get ahead of myself, photos to follow

(It's a b@#$h to get in there)

I'm off to get some plumbing supplies and give some version of all that's been suggested a try. I just wish this had reared its ugly smelly head before the upholstery was done as some parts really aren't going to be easy
To get a high point on one side, I need to pull the battery, the other, the trunk lift - which will be the easier of the two. But I knew when I built this car there was going to be some 'interesting' days, so no big deal

I'll report back so at least there will be some record that others can use

Originally Posted by IC2

OK guys, this is the vent/roll over valve that's in the tank top itself:



Mike, with a Performer carb and Carter mechanical 5-6# output fuel pump, I don't need a return line

Wasn't thinking you needed a return, just couldn't remember your setup! Since I have the same tank arrangement as you I'm curious how you correct it as I may need to repeat it on mine!

What I have done so far is to take the vent out of the tank. Evidently it can become immersed in gasoline - and was actually wet on the bottom half inch. There isn't that much gas in the tank - possibly a half tank.

I made up a well using common galvanized pipe as shown and in this order from the tank:

- 1/4" close nipple
- 1/4 to 1/2 coupling
- 1/2 x 6" nipple
- 1/4 to 1/2 coupling
- vent valve

I attached about 10 feet of 1/4" vacuum line, ran a loop to about an inch below the tank bottom, back up to about the tank middle then through an opening between the frame and body. I then ran a -6-8" diameter loop behind the fender brace.

As of 4:17, (5 minutes ago), no odor from the hose and it's 89*, plenty hot enough to expand the fuel to give off gas.

I really can't take a photo where that set up is - heck I could hardly see the arrangement.

Dave, I don't think you want that first part of your loop because if you will tend to condense vapors over time and they will settle in that low spot. I believe your hose should slope up from the vent connection to your high point, then perhaps turn down. I still don't see any value in having it drop down to tank level, but I don't think you want any low points in that line.

I think I will add a riser like yours to my trunk mounted tank, just for grins. My vent line will run up to the top of the trunk, only about 6", then drop down to a drain fitting through the floor.