You're all probably as tired of hearing about this as I am dealing with it.

My 1968 is still venting gas like mad. I can now spew gas with 1/8 of a tank on a 45 degree day.

Here's where it was at and what I've done since:

I put a fuel filter in that had a 1/4 and 3/8" inlet and a 3/8" outlet. I then added 8 feet of line, routed it around the tank, down the frame and had it exit by the license plate. This is similar to what Harold did with his '68. Still spewed with a new non-vented and a vented locking cap. All temps, no matter how full the tank was.

So, I now ran the line above the frame, into the driver's wheel well, all the way to the top, just to see if it is a siphon problem. Kinda like draining a water bed. Sure enough, it can still spew. There went the undercoating there...

Anyway, I'm now to the point of putting a vent canister into the engine compartment, running the line down the driver's side frame to it. I'd even hook up to the PCV side if I can find the right parts like the '71 up cars. BUT, I don't have the box thing that goes behind the seat like those cars. This would add 14+ feet of line and be about 1 1/2 feet higher than the tank. Now, I'm at 6000+ feet in altitude, and realize that today's gas expands rapidly, but no one I know, except '68-9 cars are having these issues. I think the earlier cars have a hard line in the trunk that runs up to the package tray and back down, but not sure if I want to do that if I get the same results.

Any ideas on this? Or should we start a pool on when, not if, it starts spewing? Does anyone know any newer car or truck who's vent cannister would work?

I'm about to give up on this car. It is a hazard, and I've completely given up on parking the car in any garage. My daughter's room is above the garage, and I'm concerned about her health, as well as mine. The fumes when driving the car are terrible.

Thanks in advance!

I can think of a couple of things that may be happening. First, you are sure the vent lines are open into the tank and that there is no positive pressure being forced into the tank? Second, the higher altitude may have a reformulated gas to allow better fuel atomization that is causing the excessive pressure build up. If that is the case, you may want to consider running a fuel stabilizer to control evaporation just like you run in stored power equipment. Also, a full or at least near full gas tank is actually more stable than one with a lot of air space. I would consider eliminating the maze of hoses and lines that are installed and just run a simple vent line from the tank. Possibly look into installing the evaporative canister like the later year cars had. But I would take the route of stabilizing the fuel first.

Just a thought, but i ran into a similar problem on my 67 elco and it turned out to be the rubber filler hose between the filler neck and the tank. It looked ok but had deteriorated over the years and the fumes were really bad.Cheap fix and worth checking out. graemlins/beers.gif

I had the same problem as Don on my '62 Vette. Check for cracked or dried hoses. Actually, they are cheap. Replace them all and have peace of mind...

Theo.

Sorry, should've posted this ealier...car has done this since I bought it 5 years ago. I replaced the gas tank and all lines with new stuff last fall hoping that was the case.

I replaced a tank on a 68 deluxe i owned with a tank from a 70 then I had this problem
the lines were a little different
so then I found a 68 tank and put it in
ran the lines the same way as original and never had the problem again
are you sure your tank is for a 68
i'm not sure but I think the vent lines do different things inside the tank for the different years

Tom,

Thanks, it is a tank for a 1968. Same as the original one I had, and it did the same thing. I really think the volatility of the new gas is causing a chunk of this at this altitude. My old 1968 didn't do this back in the 1980's.

How timely on this fuel vent issue...I just picked up a 67 SS 396 and have had several experiences with fuel leaking at the junction of the passenger door and fender. Now that I've got it up to have a look, I found a copper line that looks like it runs from the vent area of the tank (there is a short tube out of the vent pipe that runs to a 3 way - this copper line is on one end of the 3 way - don't know where the other tube runs - up above the tank?) down the passenger side frame then turns up into the inner fender. I pulled the line down & find that it is bent over - looks like an attempt to vent the tank? I'm @ 2500 feet, but in the AZ desert where it heats up to over 100 in the summer. What is the cure to this? Appreciate the help!

Dave
Have one of those cans behind the back seat if you need one. It's just laying around anyway. Often run my 72 up to 6k-8K feet and never had a problem. The 71/72 systems are sealed systems.

John,

I might take you up on that offer, since I'm not finding any out here. I assume that is some kind of a fuel/vapor splitter? From there it runs to the charcoal cannister, right?

I'll let you know in a day or so.

Thanks!

BTW,

Can anyone diagram the '71-72 system for me?

TIA!

Can't draw the system for you Dave. Maybe I can look for a link later. It's part of the ECC tank system which has 3 tank tubes versus the 2 I believe goes on your 68.
My tank has a sealing gas cap on it so no gas leaks out that through it.
If you need the part it's your for the shipping costs. Just send an email to me with "Team Chevelle" in the subject line. Believe I still have the gasket fot it also.

Here's one off a 70 Camaro with the EEC system. That tank looks to have only 2 lines off the tank and the separater looks like it's under the car versus the Chevelle that's inside. Maybe it's clearer if you print it out.
http://www.nastyz28.com/2gcog/emissions.html

David, on my 71, the can behind the seat has four ports. Three go to the gas tank and one goes along the frame to the engine compartment to a cannister which I don't have. Not a diagram but I hope this helps.

Well, this hasn't gotten any better. She just belched about 3 cups before I burped the cap. Love the smell of gas in a garage :(

I'm investigating the separator setup like the Camaro has.

I did try the stabilizer as well, no luck.

You would think that VENTS would vent the vapor off the top of the tank. Is it possable that the wrong pickup could be going to deep in the tank & picking up gas not vapor ?

ASB,

Good question, but that would mean both the stock tank and the repop new one would be incorrect.

I'm still leaning to something they put in the gas here expanding at altitude causing this.

I have read quite a few posts about this problem, and it really sounds strange.

In order for the gas to come out through the vent line (assuming that this happens when the tank is pressurized by hot weather), it has to run to the bottom of the tank, or at least below the fuel level. That could be the case with a return line, but I can't possibly think that a vent line is made that way. The end of it should be above the fuel level, or else it won't work, will it?

Without knowing much about how the tank is designed, I would try this: If you have several lines coming from the tank, you could try to disconnect them all. Then connect a hose to them, one by one, and blow air through them. If you can hear the gas bubbling, it's below the fuel level and can't be used for a vent. Just a theory, but it should be a matter of simple physics, "only" a matter of finding out why it happens...

I'm probably going to replace my tank in the near future, so it would be really interesting to hear the rest of this story.

I had a similar experience just this week. I was testing my fuel lines from the tank to the front and back (have EFI so I was checking for a good round trip under pressure) First with air for any major issues, and then using the fuel pump with gas. Everything was working fine. No problems! Then the next day, my wife calls and says there's a puddle a gas about 6' accross under the car. My son slides an empty 5 gallon paint bucket under there to catch what still is coming out. I checked everything, find no new leaks, but noticed that that I forgot to seal up the old supply tube. (I'm running a sumped tank) I was surprised that with just 2-3 gallons in the tank, almost 1/2 gallon was in the bucket!
RE: The previous posts....
I'm thinking that these vent lines are not staying clear of the fuel. I looked inside my tank while I was putting in the sump, and noticed that the vent tubes extend several inches in to the tank... running along the upper side. I'm wondering if some have been bent down or somehow not where they are supposed to be. I would think that fuel could enter easily while driving, collect in the tubing and get pushed out when pressure rises. That EEC separator looks like it would be critical in order to keep gas in the tank and still vent properly.

I own a 64 ss, small block. I have the same problem with gas coming from my vent line. Mine seams to do it more after I fill it up full and it is a hot day. I have had people tell me a red lights that I'm leaking something underneath. When I stop and check I find fuel leaking from the vent hose end. I made the vent line longer and ran it above the rear spring tower, but it still does it every once in a while. Everything in my setup is original except lines, rubber have been changed. Don't know what else to do!!!!!

Did you say at the biginning of the post that you put a differnt fuel filter with a added vent line going back to the tank? Is this the line that is leaking? Where is the filter? before or after the fuel pump? Is this a factory setup or did you change it from nonvented? If the filter is after the fuel pump the return line is under pressure. Did the car come from the factury with a vented or unvented cap?

ASB,

The car came with an unvented cap. The two orignial vent lines both spew gas. I routed them into a fuel filter and out to a longer line hoping the travel would reduce the amount of gas that comes out.

With the dead stock system, it basically wasted all the new paint on the frame and axle from the gas litterally spraying out.

I may have already replied, if duplicate sorry, how about installing a tee in the filler neck and running your vent line from the tank up to it, then extend a hose from the other side of the tee to above the tank fuel level? if your tank spews it should pour back into the tank and the other end of the tee being open to the atmosphere should vent your tank when driving? Just a thought Jim

Hi,
68 Chevelles Always had this problem. Don't ask me why some do and some don't. I know I experienced this problem with my own car almost 20 years ago with a 68 Malibu. Chevy actually had a service bulliten for this problem. Don't ask me the science of how this works, as I would not have believed that this works either unless I would have seen it with my own eyes. Their original fix was a small plastic reservoir made out of plastic that essentially had three openings, two on one side and one on the other. The two connections on one side went to the two vent hoses from the tank, and the upper single connection was open to the atmosphere. It also had a small sponge or filter on the inside of the reservoir. You just inserted it in the vent hoses and stuck the hoses back behind the clip. Whole thing was only about three to four inches long. I think this item is still there under my 68 SS Conv and I have had no problems with it. It is stored away for the winter and I cannot look at it easily. I think if I do some research I could come up with a part number but I am sure it is long since discontinued. When you replaced your hoses, was this little reservoir on there? If you did away with it, this could be your problem. What does it do? Does it provide just enough equalization of pressure to stop the fuel spillover? I don't know, but I know it sure cured the problem. Maybe one is still out there on somebodys parts car or in a junkyard that is useable, or maybe you could make one out of copper pipe. Good Luck and hope this helps.
Jeff Dotterer
68 SS396 Conv A/C Power Windows
70 SS454 LS-5 M-22

I have this vent on my 69 and have had NO problems.My .02

Here is the 69 vent for sale on e-bay.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34198&item=4536155440&rd=1

Here is the 69 vent for sale on e-bay.
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&category=34198&item=4536155440&rd=1


I can confirm that this is the exact one I used to fix my problem 20 years ago. Good job Shooter!!!!!!

Jeff Dotterer
68 SS396 Conv A/C & Power Windows
1970 LS-5 M-22

Gents,

My original '68 had one of these, and this one's was missing when I purchased it. I've not thought of getting one of these as I find it bizzare that this little piece of plastic could solve the issue. BUT, I've been wrong before....

Ground up carries the repro part of this...FUEL TANK VENT 1968-72 Code: XTV-689 Price:$39.95 and I've thought of getting this for the heck of it. I do know it doesn't come with the foam piece inside though. Would a foam like an air filter for a mower be the right stuff to use?

Question as to the science. How does this differ from my 2 inlet, 1 outlet fuel filter that is essentially the same idea? Hmmm....

Not sure why it works but.... I used foam from a mower filter in mine.

Thanks for the info & part#, now maybe mine won't drip on to the tailpipe when I brake! :thumbsup:

BL

i've been reading what some of you have been dealing with because i have the same issue with my 69,chevelle,i replaced the fuel tank thinking it was bad,rerouted the 2 vent lines with no help,even put them into atee fitting,still having gas coming out,i even put a vented gas cap on,i called ground up today an had them ship me the new plastic piece that connects to the fittings so hopefully that will fix that problem,ouch on the price for what that plastic piece cost but when you gotta have it to fix it right,i hope, bill

Gents,

I just had a long conversation with my dad who was the original owner of my original Chevelle. I was slightly wrong on what was in the original car's line. It was a bolt-like part in the larger vent line that had a hole drilled all the way through it. The smaller line had nothing in it. He replaced the vent lines on the car when it was about 8 years old due to them rotting and almost threw it away with the old lines until he realized it was there. This car lived at sea leve as well as at 6500 feet in Colorado and NEVER did this. A picture of this can be seen in the factory assembly manual.

I surmise that GM changed the design due to some cars having issues with this part or possibly that this bolt-like part may not have been part of an early car run. My original Chevelle was built in February 1968. I suppose it is possible the TSB came out later in order to fix the problem suffered by some cars in this scenario.

This current car didn't have any parts on the vent lines as they'd been replaced with what looked like cheap red garden hose when I purchased it. I've replaced everything like I said, but to no avail.

I don't understand the science either behind this, but heck at this point I'll try anything. I guess $40 for a piece of plastic if it works is a bargain after this ordeal.

The 68 Chassis Service Manual show a small device inside the 1/2" vent tube on the tank.

The good book says;

"Chevelle sedan models are vented with two rubber vent hoses at the right forward edge of tank. Hoses are attached to the tank with clamps and to the underbody.
IMPORTANT: It is important to note that the above gas tanks use non-vented filler neck caps; therefore, it is necessary to be assured that the vent hoses and lines are free from dirt and foreign material and that they are open at all times.
The larger 1/2" vent hose on Chevelle sedan models incorporates a restrictor which should be checked occasionally, ans if plugged , cleaned in gasoline and then reinserted flush with the end of vent hose."

This is on page 8-4 Fuel Tank Vent Lines
Illustrations of vents on page 8-2

Maybe this is of some value. Checked my Elky and it does not have this restrictor and it is the original gas tank wit VENTED cap.

Ok, this is probably a dumb question, but have you asked a Chevy shop? It seems like this is a common problem, so there could be a service bulletin or something with a fix. Or you might even be able to find a mechanic who has been there long enough to know?

diagrams in service manual. plugged lines are common as well as bad hoses. use a vented gas cap. There should never be any positive pressure on a full gas tank. also charcoal cannister is also an issue.

also charcoal cannister is also an issue.

68 & 69 didn't have a cannister.:p BTW I thought I had found the part that Jeff talked about, but when they went to pull it, it wasn't on the shelf. It was gonna cost me $18. Wonder if it's the one on Ebay now for $102??:sad:

BL

Not a single shop or dealer around here has ANY info on a car that old.

As for the system, no canister and a Non-vented cap is stock for 1968.

Ok,

I ordered the vent from Gup as well as a new gas cap. I'll post back how it does once it's on.

I'm reading all this, and my 68 leaks a little gas too. I'm very interested in how well the G-up part works. But, I'm still confused...

Why are there two vent lines anyway? Where do the vents "end" inside the tank? Does one line vent the front-left of the tank, and the other vent the rear-right? That's the only reason I can think of for two lines... in case the car is sitting at an angle and one side of the tank has the air "bubble" while the other side doesn't (hence, the vent is under the gas).

If one line was clogged, the car would spew gas depending on whether the gas tank was level and which side was vented. Could we try parking the car at different angles? For example, what happens if you BACK INTO your garage? Does this fix the gas spewing problem?

The part looks like a simple pressure equalizer (with a foam splash-guard). It can't be anything else. Why would there be a pressure differential between the two vents?

I'm going to make a little equalizer out of some tubing and see if that works. A PCV valve (upside down) with multiple outlets would allow venting, and equalizing at low pressure differentials, but would close if the pressure got too high (preventing spewing). But I don't know if that's a good thing.

Pete,

I've tried multiple contraptions and currently have a PCV valve on it. It doesn't keep the gas from flowing - trust me on that one.

The PCV valve was a good idea! Sorry this has been so frustrating as it's obvious you're doing everything you possibly can do.

I've noticed that when my tank is leaking (directly onto the hot exhaust pipe of course), it makes a sound like it is sucking up some air into the tank (a gurgling noise) and then it stops. It's like there needs to be some internal pressure equalization that I don't understand. If there is low pressure in the tank, why would that cause the vent to spew?

Ok, I quit. I've now got a completely stock, 1968 system in the car and it spews like crazy.

I now have a new tank, new lines, correct un-vented cap, the nice plastic part for the vent lines complete with filter material inside. The car just dropped 1/4 gallon or more all over the garage floor.

For sale: 1-1968 Chevelle that is making me sick.

So, any other wise ideas?

This is one of the weirdest problem I have heard of. This problem doesn't seem to be totally uncommon, so there must be something wrong with the design. If you're out of ideas, have you considered putting a new return line on the tank? You will have to take it out, drain it, dry it and weld or solder a new line to it, making sure that it's above the fuel level. It seems like that's a minor undertaking considering what you have already been through.

Olle,

The tank doesn't currently have a return line. So, from where would I do this? At the carb? At the pump? I've considered one, but I'm not sure where to put the thing.

Thanks.

Sorry, I wasn't really awake when I wrote that, I meant vent line. It should be pretty simple to just install a new vent somewhere at the top of the tank, or maybe even on the neck. Another thing you could look into would be if a tank from a later moder will fit. Again, there seems to be something wrong with the design if you have to fool with lines, valves etc. so you're probably better off attacking it at the tank itself.

Old cars usually have a simple line from the top of the tank as a vent, and that's it. Shouldn't have to be more complicated than that, if you don't have the canister setup.

david, read this thread. something about the fuel pump causing the problem.
david
http://forums.performanceyears.com/eve/ubb.x/a/tpc/f/4986070911/m/963604491/r/774609491#774609491

David,

I registered to see the forum, but haven't been able to get in. I'll check later.

Ok, new thought process here:

Several folks I've talked to have suggested check valves for the vent lines. Another TC member has a buddy that uses these with no problems.

So, I installed a one-way check valve in the smaller (1/4") vent and plugged the 3/8" vent. I only did this because I couldn't find a 3/8" one locally. I'm not worried about one line being plugged as they both chug gas out.

In theory, this should allow air in as the fuel in the tank is depleted by the pump. It would not allow fluid out of the tank. The negative that I can already see is that no air could escape the tank. BUT, is that such a bad deal since the pump is pulling from the tank? The check valve would allow air in to replenish the tank.

The other downside is what will happen when I fill up? I'm assuming I could keep having the auto-shutoff on the gas pump keep stopping due to excess pressure in the tank.

Anyway, a first stab at this. Optimally, I'd like an inline 2 way check valve to allow air both ways and stop the fluid.

I'm currently driving the Chevelle today, so I'll have an idea if this at least might be feasible.


Thoughts?

Well, that lasted two days. The tank expanded like a balloon without being able to vent.

NEXT!

have you read the PY forum thread, yet?
it mentions the return from the fuel pump causing the problem.
guy says his fuel pump was putting too much back to the tank. obviously it had to be air to cause the spilling of fuel out of his vents on the tank.
he replaced the fuel pump and all is well.
if you haven't done so, i would replace the fuel pump.
heck, you've changed everything else.
is the new tank damaged?
david

here's the piece from the PY forum.
Looks like I found the problem! It was the fuel pump.

Friday was really a nice day, weather wise, so I took the opportunity to replace the pump. When I removed the pump, the first thing I noticed was what looked like a black rubber band hanging out of the fuel inlet. That can’t be right!

Also, the pump didn’t have any weep holes, so if it were going bad, you would never know. On the side of the casting was a date circle with “85” in the center. I assume that means the pump was manufactured in 1985.

I think what happened was the pump seal went bad (maybe from age), and was forcing fuel (a lot of fuel) through the vapor return line. It was difficult to tell if the oil had gas in it because the car always had a gas smell around it from the fuel tank.

After installing the new pump, the car started up with out pumping the gas (something I had to do often) and ran fine. I checked the fuel tank after a test run and I didn’t have any signs of fuel leaking anywhere or that strong gas odor.

I’m planning to take apart the old fuel pump just to see what went wrong.

dave,
this was a 70 gto with a return line to tank.
he mentions he does not have the EES? system.
but his car was pushing fuel out of the vent and gas cap.
david

David,

Thanks for the leads. I actually spent a few hours over there reading the other night. Great site!

However, yep, he's got a return line. I'm about ready to replace the pump, but not sure it'll do much. I've got 3 different shops (good ones) telling me it could push pressure down the 1 fuel line, no it won't, and maybe.

AAAAAAAHHHHRRRRRGGGG!

I realize this might put more pressure into the tank, but what about adding a return line via a filter and running that back to the tank?

I had a slight problem like yours. Not as bad though. On my 69. Had it off the frame and had removed the retun line from the frame. Never reinstalled it. I plugged the tank stub. Had a problem with gas on the floor, from vent line. I used 4 plastic fuel filters. On the tank. I put 2 in the vent line stup. Put 2 in return line stub. They are standing straight up, next to floor boards. This solved my proplem with gas on floor. I still get a faint smell of gas at different times. Can hardley smell it. This might work for you.
I hate to see you sell it because of this problem. LOL
Good luck with her.

Ok, the latest saga...I drive home, and she's starting to kick and buck, meaning the tank is expanding rapidly. I stop and hear squealing from the cap since it's trying to vent around it. I burp the tank and leave the cap off for a few minutes. Put it back on, start the car, wait a few minutes, and take the cap off. The cap wanted to blow out of my hand. Now mind you, this is while only idleing for a few minutes!

So, off to the house, and I bypass my fuel pressure regulator for the heck of it. Drive the car for a few minutes, pop the cap and there was VERY little pressure at the tank. Hmmm. Remove the cap off the vents, take it for a long spin, bark the tires a few times, heat it up real nice like. Pull into the garage and shut off the car. No gas. AND I don't smell anything other than a car that has been driven hard.

Moral of the story: I have no freaking idea. I'm so used to getting my hopes up that I won't do it this time. I've got 1/2 a tank of gas and tomorrow is going to be warm again, so we'll see.

Stay tuned to the same bat-time, same bat-channel...

Update: Well, so far, no spew. I just got back from driving all over at speed, in traffic, etc. Obviously no build up as the vent is open.

So, if this actually works, why would a regulator give the pump fits? Unless the pump is unable to handle being "stopped down" by the regulator and can't handle the pressure?

why were you using a regulator?
david

Mechanical pump, gas needs somewhere to go???????

David,

I had an issue at one time that the carb was getting flooded out constantly. The pump before this one was running 7+psi. Edelbrock only recommends 4-6 so we put one in about 4 years ago.

As for gas having no where to go, I've alwasy thought that.

Ok, two days, warm weather, altitude changes, and it won't spew yet. So, while I'm not calling it a trend, so far, so good. I realize I've thought that before, but who knows.

I'll be gone for a week, so I won't get to test it until I get home. Besides, we're suppossed to get dumped on with snow starting tonight.

And whatever you do, don't try to "clean" that 1/2" hose with the restrictor in it (the one on the passenger's side of the tank) with carb cleaner! I did, and the foam slid out of the hose like a chunk of lung hack!!! So I had an "un"restricted hose that I couldn't find a replacement for. Used a spare K&N mini-filter with lawn mower air cleaner foam as a pinch replacment.

just finally recieved my ground up part that goes on the 2 fittings on the 69 chevelle fuel tank,hopefully the 39.00 dollar part fix's the gas leak that i'm having,i did not know that this was a fix from gm back in 68 & 69. bill

Ok, with the pressure regulator out of the system, the car DOES NOT spew gas. It vents, and I can occasionally smell it, but there is no fuel coming out. It was 75+ yesterday. I even ran back and filled the car up to see if that would force any spewing. I'll drive it again today into town to see how she does, but at this point, I'm about 90% sure we're done spewing.

HOWEVER, now the carb seems to flood when sitting. I'm getting a higher gas smell under the hood and it's harder to start when hot. This is running a stock fuel pump.

Anyone know what the stock pump rating for flow is?

How does the pressure regulator force gas back down the fuel line at the same time the pump is drawing? No idea. However, at idle, with the regulator, the car would build a heck of a lot of pressure in a very short amount of time.

Thanks for putting up with the insanity.

Dreinekie I guess I'm not understanding. Did the car have just the one gas line or did it also have a return line?? I still think that the extra vent lines need to be checked to see they are above the fuel level so that they vent fumes not gas.

I'm having this problem also. Anyone have an old gas tank that they can open up to see how things work?

I'm having this problem also. Anyone have an old gas tank that they can open up to see how things work?

That's what I have been thinking ever since this thread started. I have actually been seriously tempted to go to the junk yard and get one, just to find out. I'm thinking about replacing my gas tank, but I don't want to run into a nightmare like Dreinecke's.

Well, this hasn't gotten any better. She just belched about 3 cups before I burped the cap. Love the smell of gas in a garage :(

I'm investigating the separator setup like the Camaro has.

I did try the stabilizer as well, no luck.

Hope you don't have a gas water heater in your Garage !!!!!

Nope, in Colorado they go inside the house :)

As for the venting problem, it is completely gone. Nada, zippo. I'm going to finally pull the regulator off the firewall this weekend and am totally p'od that I even mounted it there. Oh well, live and learn.

Meant to follow up on this: the sucker is doing it again! Gas, gas, everywhere...

I love this thread! NOT!

After talking to another '68 owner about his woes, I drove the car last night.

Here's the current setup on the car: All stock parts, no regulator to the carb, the factory repop white vent part installed for both lines, new gas cap that is the stock, non-vented one. Just like the factory made it all the way to the carb.

I took my daughter to guitar lessons at 8pm. The temp was 19 degrees . The tank is a third full. Drove it back home, put it into the garage, and guess what? She upchucked several cups of gas on the floor.

I'm begining to have a theory here:

1) The original '68 design sucked. Vent lines went deep into the tank perhaps?
2) A new tank with revised vent lines was created. This could have replaced certain ones at dealerships under a TSB type of scenario.
3) Some cars got the new tank, most didn't as they were using remaining stock at the factory. The inventory spilled into 1969 at some plants.
4) Repro companies got the "Bad" tank design and are now selling it to us.

Hypothesis: Due to the mid-to-whenever year tank change, some cars got it and others didn't. Hence the reason some '68 and '69 cars do this and others don't.

I'm off to find Scully and Molder...I'm sure they'll have some info for me

I didn't know about this problem until I started following this thread many months ago. And then one day I went to town and got a full tank of gas, went home, backed up and parked the car in our driveway, and you know what: Two hours later, I saw gas dripping from the vent tube.

I hold you responsible for my emotional trauma. If I hadn't read this thread I would never have noticed.

wow:confused: ,in the last post i bought that white plastic vent and i have'nt had any more problem the rest of last year,we had a lot of hot days over here,i wondered if anybody cut open a old tank to see how the lines are inside? bill

Just to put my .02 cents in.
I have a 69 el camino with the same problem. I have two lines coming out the top of the tank. When I bought the elky they had put a newer year nozzle (with the small hole for unleaded fuel) with a rubber boot jointing both pieces. The vented line was spewing little fuel on hot weather or when the tank was full. I drilled a 1/8" hole in the center of the non-vented plastic gas cap and sealed the vent tube. No more gas spills, but every once in a while I can smell gas fumes. I was also told that they made a fuel pump for that year that had two inlets from Napa auto parts. I have one outlet. When I have time I'll purchase the one w/two and find out if that solves the problem.

wow:confused: ,in the last post i bought that white plastic vent and i have'nt had any more problem the rest of last year,we had a lot of hot days over here,i wondered if anybody cut open a old tank to see how the lines are inside? bill
Yes I did-- check here-- http://www.chevelles.com/forums/showthread.php?t=106519&highlight=gas+tank+vent

BillL

bill, thanks for the pic,i always wondered how the lines where inside the tank:confused: ,they should have continued the fuel tank set up from 1967 chevelles to 1970 models then make a change after 1970, bill

I had the same problem with my 69. It had the original set up, the white plastic piece on the 2 vent lines coming from the tank and a non vented cap. It spewed fuel all over my frame and tail pipe. I used foam from a lawn mower filter and re filled the plastic piece. It still spewed fuel. I took the whole thing off and put a canister type fuel filter in place of the plastic piece and ran fuel line from the canister across the top of the tank and wraped it around the filler neck. It worked.

Interesting post about the fuel pump, I did change the fuel pump on mine for another problem and maybe that was the root cause of the fuel problem. I used an AC Delco pump as a replacement. Now that someone is repoping the plastic piece, I may try and put it back to original.

Diamond Judge, thanks for the post, it answered some questions I have had for a long time.

I'm baaaaaaaack!

Yep, still a problem. I've had the car out several times over the winter and had mixed results. I'm still running a dead-stock system. Yesterday hit 65 and she was spewing her guts everywhere on less than 1/2 of a tank of new fuel. I would jump out and burp the tank at every place I parked, and before I could shut her off and get to the gas cap, she was already purging.

So, I'm finally off to go get a new fuel pump. At this point, there's not much else to try. I do have a friend who got the fuel/air separator out of a 1970, I'm just reluctant to punch a hole in the trunk floor to try in and not have it work.

I'll let you know what happens after the pump. I'm planning on getting a stock AC/Delco unit. The current one is a generic from a Big A parts store.

Stay tuned, this is probably NOT over...

Did you ever try the test of blowing in each of the tank vents to listen for gurgles?

Do both vents flow air freely?

The design intent is for at least one of the vents to be above fuel level. Which means one can be below. Which means one could flow fuel into the seperator. Which means the seperator must be high enough, and the vents free flowing enough, that fuel never flows all the way to the seperator.

I would not count on extra fuel line length accomplishing much here as the volume is rather small. A larger seperator would be more useful. A water filter cannister could be perverted to create a larger seperator.

If the vents flow freely, one vent is in air, and the seperator is above fuel level, it should not be able to push gas out the vent. But plug or restrict a vent or get the seperator too low and all bets are off.

This basic vent operating model is even used with the EEC tanks in '71 except that the number of vent lines, and thus vent positions inside the tank, was increased from 2 to 3. Interesting also is that the seperator, at least on the El Camino, contained something that clunks. I suspect it is a float to shut off the vents if excessive fuel collects in the seperator.

Did you ever try the test of blowing in each of the tank vents to listen for gurgles? - Yes

Do both vents flow air freely? - Yes

I would not count on extra fuel line length accomplishing much here as the volume is rather small. - I actually took this off a while ago as I found the same to be true on my car.

Thanks for the input. This has really been an insane hunt for the cure. I just got a new Fuel Pump, so I'll strap it on tonight and see what she does. Funny enough, today is warm, I just drove around, and no problems.

I'm going to need some serious therapy when (if) this is over...

I'm not proud of the asthetic value, but it works:
http://www.chevelles.com/showroom/data/500/vent.JPG

http://www.chevelles.com/showroom/data/500/vent2.JPG

To burp you have to be A) get fuel up the vent line(s) and B) not allow it to drain back. You also have to have enough fuel to overwhelm the seperator.

You could get it up one line under acceleration and the other under deceleration or alternatively left and right hand turns of sufficient enthusiasm.

I might expirement with clear plastic tubing on the vent lines to see if you can determine if you have gas in one or both and if it can drain back.

Thanks for the help as always. Good pics BTW!

Update 3/22/07 (#459?) - New fuel pump on, 60-70 degrees, 1/2 & 3/4 tank driving - no spewage. Barometer close to previous days last week when it spewed.

I am noticing very little pressure at the cap after just parking it than before. So, we'll keep on watching and waiting.

Thanks for the help as always. Good pics BTW!

Update 3/22/07 (#459?) - New fuel pump on, 60-70 degrees, 1/2 & 3/4 tank driving - no spewage. Barometer close to previous days last week when it spewed.

I am noticing very little pressure at the cap after just parking it than before. So, we'll keep on watching and waiting.

Any updates? My 68 has had the same problem tried all the same things :sad:

68chevyred -

Well, it's warm out today, I've driven to work, and just put a full tank in her. We'll see how she does on the way home tonight. I'll post back when I get there. My fingers are crossed...

Well I can tell you one thing when I started up my engine like this I put the air vent tube in the gas tank in the picture and while the engine started up it pumped quite a bit of fuel in to the spare gas tank (not pictured).

The first time I started it up I used 2 gas tanks one with fuel and one was empty for the vent tube and it pumped alot of fuel through the vent tube and had nothing to do if the car was moving mine was just sitting their.

Note: I did not have a pressureized tank during this..

http://img266.imageshack.us/img266/8867/p1010414fj4.th.jpg (http://img266.imageshack.us/my.php?image=p1010414fj4.jpg)

Well, one day does not a trend make...got home, smelled gas. Expected a mess, walked around to the back, got vapor, no gasoline. So, we'll try it all again tomorrow!

Thanks for the update let us know how tomorrow goes :yes:

Came into work today at 45 degrees (an 800 foot elevation change from my house) and didn't smell anything like I normally do. It should be warmer this afternoon, and so I'll run her around a bit and see if I can get it to spew.

Like I said yesterday, I could smell it venting, but there was no liquid anywhere. That is an improvement if it holds...

Well, it's cooled back down to the 50's, but she's spewed at 35 before, so I'm not sure what to think. I guess I'll just have to keep driving it!

David, Do you got a part number on the fuel pump? What is the difference in the pump? Thanks Ed

Ed, I just ordered the pump at the Napa store and told them it was for my 327 (it currently has a 350). I'll see if I can dig up the number for you when I get home. As for differences, I can't see any from the outside.

I've not driven it for a few days due to snow and ice, so I'll have to try it out again in a day or two when it warms up.

Thanks Dave,
I am hoping that it takes care of it:yes: Do you know if small block and big block pumps are the same? as i have a 396 in mine

Ed,

I can't find the dang reciept! I looked again last night, so I'll see if I can get it off the part itself.

Interestingly (or not after 7 pages...) I can't get it to spew gas right now no matter what. I drove the heck out of it yesterday in 65+ degrees, over 100 miles, up and down 1500 feet in elevation with a 3/4 full tank. Got home, smelt gas fumes only, no spew. I'm actually crawling under it to make sure it's not going somewhere else. Vapor smell was gone in a few minutes, not the hours like when it spews. I've still got my fingers crossed...

Well so far it is sounding positive. I'm willing to change the pump if it will stop it from spewing. Thanks for the update

Ed, still going well with no problems. Drove the heck out of it again on Saturday. I'm really thinking this might have fixed it.

Well, this may jinx it, but THE CAR DOESN'T SPEW GAS ANY LONGER!!!!!!!!

Holy cow! I'm still dubious, but it just won't do it at all. I've driven in all conditions, temps, etc.

New fuel pump, whodathunkit?

There is something to be said about going back with the original design if you have strange or persistent problems. I'm learning this the hard way while conquering my overheating problems on my 68 BBC, believe it or not cowl and hood seals and dust covers on the innerfender's help eliminate problems when they are installed.

There is something to be said about going back with the original design if you have strange or persistent problems. I'm learning this the hard way while conquering my overheating problems on my 68 BBC, believe it or not cowl and hood seals and dust covers on the innerfender's help eliminate problems when they are installed.

Your 68 looks good finished....nice job

Thanks Leo,
It's 98% finished but may not ever be completely finished, I don't know where all this restoration stuff end's.....Les

the gas tank in my 68ss had two vent tubes coming out the top of my tank with two rubber hoses that just dead ended. no repo tanks are available with that same vent.try to get an original tank.

Hate to dig up a dead dog, but the spewing problem that I solved by replacing my tank and pump and sender has returned. I am guessing my pump has gone bad? But it is only 2 years old or so. Great design GM.... just great.

Still spewing. Anyone know what size hose fits the larger vent, and where to get it?