Gas Tank Connections on '69?

Okay, my gas tank is out of the car. I am trying to fix the "dump a gallon of gas on the ground whenever I fill up" problem.

I see two connections on the sending unit-
- a 3/8"connection, this is the pickup.
- There is another connection (1/4"?), what is this for? It appears maybe to be a vent.

Then there are two connections over toward the passenger side of the tank.
- One small connection (5/16"?)
- One larger connection (7/16?)

I bet that most of these should get plugged, but I am curious what they should be used for (even if only in different years). Vent? Return line? Feed to the charcoal cannister? The more I understand, the better I can fix this problem.

TIA,
-Bob Cunningham
bobc@gnttype.org

 

gas tank

bob, i have a 1970buick chassis service manual that has a pretty explicit section on the fuel tank and lines. what kind of car do you have and what year is it?

 

Duh, sorry.

The car is a '69 Special.

However I am still curious how the '70 should be plumbed, the more I can learn the better.

-Bob Cunningham
bobc@gnttype.org

 

gas tank connections

bob, sorry im late getting back to you, had to work late. lets start with the sendng unit. the 3/8 line is the supply to your fuel pump. the 1/4 line is the vapor recovery to your fuel pump. the connections on your fuel pump are the same size as your sending unit. connect 3/8 to 3/8 and 1/4to 1/4. the 2 outlets on the side of your tank are for venting each corner of your gas tank. they prevent fuel loss due to expansion of trapped air. i would not block these vents off. hope this helps you out. john l.

 

John,

Thanks for the response. It helps me some, but still leaves me very puzzled.

My car doesn't have a vapor recovery (and never did, as far as I know) so I am going to leave that blocked.

As far as the two vents on the side go (they are both on the passenger side, BTW) I don't know how those vents are supposed to prevent fuel loss, since they dump fuel all over the ground! Those are the outlets that I don't understand. If I don't block them off, I am going to continue to leave big puddles of gasoline whenever I park on a full tank.

I would like to leave at least one port open somehow, but since I can't figure out how to keep gasoline from dumping out I am gonna have to try sealing all of the openings and seeing what happens.

I have been trying to solve this problem since 1989, but so far I have run into noone that can tell me how to stop this problem (although I have talked to others that do have this same problem). Thanks again for the help, John!

-Bob Cunningham
bobc@gnttype.org

 

gas tank

hi bob, there should be a baffle in your gas tank which is supposed to block fuel from those 2 lines on the side. if the baffle is cracked it will allow fuel instead of just vapor to leak out of the lines. i would look for another gas tank. if you cant find one from a salvage yard try poston or year-one. good luck

 

John-

I will have a look.

However, you should know that I replaced the gas tank about 5-6 years ago, and the problem existed on the old tank and there was no change with the new tank.

Also, the gas usually leaks out while I'm parked, it slowly dribbles out for the first hour or so (as pressure builds up in the tank on a hot day after I fill up with gas from the cold ground). So it's not a "sloshing" problem, and I can't see how a baffle would help that.

The tank is still out, I will have a look with a mirror before I reinstall it.

-Bob Cunningham
bobc@gnttype.org