Gas tank trouble

[v8frank]

Hi guys,

I am fighting gas tank troubles since I got my car about 4 years ago. Every time I do a fill up the vent lines will overflow.This problem persists to this day even after I did all of the below!

But let me first give you some details of the car.
It's a '69 Sat cloned into a very well made and detailed A12 Runner. This includes a great performing 440 with a six-barrel set-up on top of it.The rest of the drivetrain consists of a TKO-600 5 speed and a Dana 60 with 4.10 gears.(hence the TKO)

The gas tank had been replaced before I got the car. The sending unit is a new 3/8 " unit with a 1/4" return line .Main fuel line is 3/8". The return line was pluged off when I got the car because there was no return line to begin with and no fuel vapor separator near the fuel pump either.
When I got the car it had the 2 original vent lines connected to the tank.The short u-shaped one that goes up and comes down again plus the one that goes into the trunk and comes out again on the passenger side and ends up in that sides frame rail.

The first time the overflowing showed up caused the short vent line overflowing. Which makes sense as it is the shortest way for the gas to get out.
Right after this I got the car on the lift to check the vent lines. I found out that the long vent line was clogged by using compressed air. I took it out and I could manage to clean it out.
I was sure that solved the problem.....until the next fill-up!!!:angryfire:

In the meanwhile I have added an original fuel vapor separator next to the pump and a 1/4" return line connected to the sending unit.

I got then in touch with a well known Mopar guru from a well known Mopar magazine and after sending him some pictures from my vent lines on the tank, he suggested to remove the short vent line thinking of it only necessary for California emissions set-up !
So I plugged off the short vent line connecter on the tank and after the next fill-up the long vent line now overflowed into the frame rail and on to a buddys driveway.
The quantity of overflowing gas is extreme ! I would easily guess at least half a gallon.:icon_eek:

After the last fill-up I did, like 2 weeks ago, I backed up the car in another friends driveway with a very, very slight slope say almost level and when I opened the fuel filler cap I had almost half a gallon of gas coming out before it stopped. A couple of hours later it still had leaked on the floor through the long vent line.The gas cap is an original replacement and is like the original cap NOT vented!
Once the fuel goes below a certain level everything is fine of course.

I checked the vent line connections on the fuel tank ,blowing some air into them and I could hear and feal the air as I had the sending unit out again.(tank empty) Thinking that maybe the vent lines might be clogged in the tank, but no.

The fill-ups work absolutely normal;no slush back etc.etc.

I have found literally dozens of people in different forums, that own especially '68 to '70 Runners or Sats for that matter,that have these kind of trouble with their gas tanks but nobody ever comes up with a solution to this problem!!! :confused5:

I have seen drilled fuel caps on several cars and other crazy stuff to solve the problem.

I hate the idea of doing crazy things with gas vapors but I hate the idea of an overflowing fuel tank on my car even more.Think of somebody throwing his cigarette butt on the ground at a car show.!!! Whazzzzaaaaa.....:angryfire:

Is it expansion of the gas, due to temperature differences, in the tank that is causing it ?
But then how can it build up pressure in the tank high enough to make the long vent line fill up with gas and then overflow?! How could it do that when it is ventilated?
Is the problem caused by a bad or incorrect reproduction gas tank ?
Could the vapor separator cause somehow additional pressure build-up in the tank from the pump?! But it did it before I added those!

What did people do back in those years that were living in the San Francisco hills? Parking their cars with the front downhill ?! :icon_confused:

I'm speachless and frustrated !:sad2:

Anyone with a real solution to this ?

Thanks.

Best regards, :hello2:

Frank

 

[v8frank]

Nobody with those kind of problems around here ?:confused:

 

[Dennis H]

69 Coronet R/T here. Don't know that I can help, but did have similar problems for years. Seems like if it was parked nose down after fillup, it would leak at the top/front of the tank. Got a 70 tank, pinched off one not needed tubes and ran the tube in the trunk higher, almost to the height of the rear deck. Seems ok now.

 

[Mr Belvedere 30144]

Maybe this will help.




http://forums.moparmusclemagazine.c...l-discussion/68-charger-fuel-tank-vent-issue/

 

[Dennis H]

Link did not work, maybe it's the iPad.

 

[Mr Belvedere 30144]

Sorry about that but it will work now.

 

[v8frank]

@ Dennis H,
I was thinking at raising the level of the vent line but I don't like the idea of having those fumes in the trunk area !
So you still had trouble even after replacing the tank with a new unit ?

@Mr Belvedere 30144,
Interesting link but seems to concentrate on Chargers which have quite a different set-up with the vent line going into the filler tube. I guess the high volume of the long filler tube probably takes care of the expansion volume of the fumes!?
I have a few buddys with Chargers but none of them has gas tank troubles.
But thanks anyway.

 

[v8frank]

News on gas tank trouble




Ok here's some news on my problem!

I was thinking about what the 2 vent lines look like in the fuel tank so I took out the filler tube and rubber seal to check if I can get some insight into the tank without taking it off .

What I realized is that the long vent line seen in the first picture( I know they're not great) is detached (soldering seems loose) from the top of the tank and goes down at least 1 " from the top of the tank.
As I had the long external vent line, going up into the trunk area and ending in the right frame rail,attached to that connection I guess that, when the fuel tank was really full,the fuel got sucked out as soon as the slightest pressure built up in the tank.:confused:

What I did now is change the external vent line to the other connection on the tank (which is the short line on the right side in the tank seen on the 2 nd picture ) as that one is closest to the top or ceiling of the tank.

But I still have to fill her up again to see if that helped !

I'll keep you posted. :thinker:

Frank

 

[SublimeSixpack]

So did you come up with a solution to your problem? I'm having the same issue with a 1968 Coronet. It's annoying as hell!

 

[v8frank]

Sorry, but I did'nt have the time to check if it works now!
I'm actually out of country for the next 3 months.
But I'll get back to it,promised!:icon_winkle:

 

[v8frank]

Hi all,


I finally had a chance to take the car out for a trip.

Filled up the fuel tank without overfilling !

Still found a couple of fresh fuel drops under the right side frame rail! (where the main vent line goes in)

So I'm back to zero and totally speachless ?!?:angryfire:

Any thoughts from someone else? :icon_question:

 

[69redrunner]

Had similar issues a few years ago. Found a rubber hose between the gas tank and vent tube was pinched. I loosened the clamps and repositioned the hose and have not had any issues since.

I have wondered from time to time if a vented gas cap would help?

 

[v8frank]

Hi 69redrunner,

All my fuel lines and the rubber hoses have been triple and quadruply checked, in fact everything is new!

You're right the thought of a vented fuel cap came to me as well but then again the OEM set-up consisted of a non ventilated cap!

On the other hand I'm a little afraid of using a ventilated cap because of possible fuel spillage when the tank is full !?
(as low as the filler tube is !!!??)

Anybody else having this persisting and pesky fuel tank problem ?

Thanks anyway for your input ! :headbang:

 

[69redrunner]

Before I crawled under and found the pinched hose, I just loosened the gas cap when I parked the car. Kind of a pain in the ***, but it did prevent fuel from being pushed out the vent tube. Which is why a vented cap may help in your case.

 

[mopar 3 B]

Think you need to find what ever is presureizing your fuel tank as it vents to atmosphere and system should take care of normal expansion. Find the heat source that is causing the excess expansion.

 

[SublimeSixpack]

Hi 69redrunner,

All my fuel lines and the rubber hoses have been triple and quadruply checked, in fact everything is new!

You're right the thought of a vented fuel cap came to me as well but then again the OEM set-up consisted of a non ventilated cap!

On the other hand I'm a little afraid of using a ventilated cap because of possible fuel spillage when the tank is full !?
(as low as the filler tube is !!!??)

Anybody else having this persisting and pesky fuel tank problem ?

Thanks anyway for your input ! :headbang:

I still have this issue with my '68 Coronet. FWIW I had the tank out, checked both vent lines inside the tank and they were in place and attached as they should be. Couldn't find anything wrong with the set up.
At this time I took the opportunity to modify my sending unit with a vapor return nipple, then installed a 1/4" vapor return line with a vapor separator at the pump. This resolved the fuel vapor lock issue I was having with the engine, but of course didn't affect the tank issue (I didn't expect it to).
If I fill the tank and park with the nose down on a hot day pressure builds in the tank and it comes out the overflow/vent. Since I couldn't find anything wrong with the system (except maybe the design) when the tank is full and the outside temperature is high I park with the nose up and no problem. If I'm at a car show and the nose is down I just loosen the gas cap until I'm ready to leave. I'm sure one could come up with a modification to the system to eliminate the issue but with todays fuel being such a witches brew I'm not going to bother. I've learned to live with it.
And I'm pretty sure if you used a vented gas cap you'd have fuel getting past it, with the filler neck being so low.

 

[v8frank]

To 69redrunner,

That's exactly what I doo when I go to a car show and park the car for a couple of hours! Taking of the gas cap does take care of the whole pressure build-up problem but it still does'nt make sence to me why a perfectly working vent line (checked many times;not clogged or pinched etc.etc.) does not prevent a pressure build up !?!
I still don't like the idea of a vented(drilled?!?) gas cap !?!?:confused1:

To mopar3B,

The car is totally original concerning drivetrain,exhaust and fuel system. I do use the original 1/4" return line with a vapor separator at the original fuel pump. All lines are triple/quadruply checked with air pressure although all,literally all of the components are new!
There is no 500 c.i. super duper strocker motor in the car that would build up unusual heat. The exhaust system is all original to the extend of using OEM repro mufflers and complete exhaust system with hipo cast iron exhaust manifolds.
So where would that heat come from as the problem is not limited to summer/high outside temperatures. Engine temperature is perfect!
Nevertheless I appreciate all input! :icon_cheese:

To Sublimesixpack,

I actually experienced exactly the same . Always had this problem and adding the return line and vapor separator did'nt help it but I thought it still might be a good idea to add it.

I'm coming to the same point of thinking that the OEM design causes the trouble by itself although why are there people out there that do not have this kind of trouble with their B-bodys!?

Yeah, nose down most definitely will cause it to leak but I even experienced the same with the car level.Don't even think about opening the fuel cap with the slightest incline to the rear of the car !?!? Gas shower garanteed!!:angryfire:
Guess I have to learn to live with it too!?

Mh,mh...may be a vent line with a bigger diameter would help ?!?

 

[coloradodave]

Reading about your problem got me to wondering if the location of the vent lines inside the tank is above the level of the fuel? After you fill the tank can you attach a hose to the upper end of the vent line and blow into the line while listening for bubbles through the filler neck? Maybe the vents were installed incorrectly from the factory and the aftermarket companies copied it....who knows. If so, this could be easily fixed by a radiator or hot rod shop. Good luck.

 

[meskip]

I know I'm really late to this party, but I agree with the last poster. The vent lines have to be getting covered with fuel with a full tank causing any expansion to push out fuel instead of air. It would seem adding a vent line near the top of the filler tube would maybe solve the issue, however finding a place to extend it high enough may be a problem.

 

[st63]

Another one really late to this....but I've had the same issue. One thing I've found out is that some of the reproduction tanks have the internal vent tubes in the reverse order of the originals...in other words, the short external tube needs to be connected to the long internal tube, and the long external tube to the short internal tube. If you just reconnect the short tube in it's original position without making sure it's going to the longer of the two inner tubes, it will leak!