Gas Tank Connections on '69?

B

bobc455

Team Member
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I have a '69 Special Deluxe. It came from the factory with a 350-2 / 2-speed, no A/C.

Ever since I can remember (I've had the car since '86), the car dumps about about a gallon of gasoline out the vent tube after I fill up. It happens while I'm parked, so I know it is a matter of expansion and not fuel sloshing.

The gas leaks out the vent tube on the passenger side of the tank.

There are four connections on the gas tank. The only one that I am sure about is the 3/8" connection on the top of the sending unit- that goes to the fuel pump. I would appreciate it if someone could explain the other three connections:
- A 5/16" (?) connection on the sending unit
- A small (1/4"?) connection on the passenger side/front of the tank (this is where the gas leaks out)
- A Large (7/16"?) connection on the passneger side / front of the tank

I don't think I should just block all these connections, because since that car has a non-vented cap there has to be somewhere for the tank to **** in air as the gasoline is sucked out. There also has to be some way of venting off fumes to avoid huge pressure building up (especially on a hot day after the gas is pumped out of the cold ground).

I tried to find a vented cap to fit the tank, but none will fit (I am told this was intentional so noone would put a non-vented cap on a tank that is supposed to have a vent).

Oh, and in case you are wondering, I installed a brand new gas tank about 5 years ago, so it's not a matter of having a leaking gas tank or something. Of course I installed the new tank the same way the old tank came out, which explains why the problem carried over. I have also changed engines (still non-AC) to a 455, removed the carb and installed fuel injection with a return line from the regulator, and there has still been no change. (I have the return line going to the large connection on the passenger side of the tank)

I am sick of dumping gasoline on the ground after every fillup, and I appreciate any insight! I'm sure Buick didn't design to work this way.

-Bob Cunningham
bobc@gnttype.org
 
The 2 lines going to the sending unit are the supply and return lines; the 2 on the front passenger corner are for vents they are normally run up the side the framerail and are attached with a plastic connector. They probally leak because:
-they are too short,they should have lines about 8"long
-the car is parked on a slope
-the lines are cracked
 
Thanks wildcat.

Actually on Friday night I had the opportunity to look at a completely unmolested, original '69. It was exactly as you describe.

I didn't understand why there were two vents until someone explained that the larger vent is actually a tube for the drivers side, and a tube inside the tank brings the fumes over to the drivers side.

I had taken the vent tube and played with that over the years- longer hose, put a cannister-style fuel filter in the hose to absorb about a pint of gas (trying to minimize the overflow), yet it still seemed to travel all the way up the tube and on to the ground. There is a *lot* of gas dumping out!

The interesting thing is that on the "unmolested" car, there was evidence of gasoline leaking out of those vent tubes (the undercoating was washed off). I guess that leakage was tolerable to Buick back then!

Anyhow, I am gonna play with this and see if I can minimize the leaking. Thanks for the help!

-Bob Cunningham
bobc@gnttype.org
 
I'm right there with you, my 69 Skylark does the
same thing, so it's a safe assumption that the problem is pervasive to the vintage. I've grown accoustomed limiting fill-ups to 10 gallons.

Good luck.
 
Pestorias,

My current experiment is with a new gas cap, and I drilled a very small hole (the smallest drill bit I had). This will allow air in to replace the sucked-out fuel, and will allow fumes out on a hot day. So far, no gas spillage, even under acceleration (just because the hole is so small).

I'll let you know if I deem this "successful".

BTW I kept my original gas cap in tact so that I can use it if I even find spillage to be a problem (like at a dragstrip or something).

-Bob Cunningham
bobc@gnttype.org
 
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