70 buick gas tankVents

[Guest 70 Buick Electra 225]

Just replaced my 70 Buick Electra gas tank sending unit with another old one for the gas guage to read again. Upon Fillup I noticed a leak not from sending unit lines but on top of the tank. It only leaked upon fillup. Do the 25 gallon tank vent hoses (two different sizes) hook up to anything? We could not find any hook ups for those two hoses on the side. No caps so I put plastic screen over and hose clamped them to keep wasps from building in there. Were there any type of caps in the past that may have fallen off? Thanks Randy

P.S. For the future anyone rebuild the 70 buick electra sending unit or sell a new one?

[Guest]

All 1970+ cars have a closed fuel system. Your car should have a vapor recovery system. A Carbon Canister with a filter should be in the engine compartment to keep vapors from venting to the atmosphere, one of the vapor lines go back to the tank. Your Buick's should look like this;

http://thumbs2.ebaystatic.com/m/mT4ER5oiKajM807JDOtKQ3w/140.jpg

You should use a GM Buick service manual to see how it's hooked up.

Your car should have three lines coming from the tank. 1. Fuel supply to engine. 2. Fuel return line from engine. 3. Vapor line going to the charcoal canister.

Edited October 30, 2012 by helfen (see edit history)

[Guest 70 Buick Electra 225]

Thanks for the info. My Buick electra is different from the other you just mentioned with three lines going to the sending unit. It only has two. To the front of the tank and on the top right corner are two breather lines. I do not see any connections going anywhere on it. Thanks again. Randy

[Guest]

Thanks for the info. My Buick electra is different from the other you just mentioned with three lines going to the sending unit. It only has two. To the front of the tank and on the top right corner are two breather lines. I do not see any connections going anywhere on it. Thanks again. Randy

First I didn't say sending unit. But just three lines. They are usually all at the sending unit. My 69 Pontiac ( last year for the vented tanks) has two lines from the sending unit and one vent line at the neck of the tank. The one at the neck of the tank is the vent tube. From 1970 that vent line is by hose connected to a hard line and run along side the fuel supply and the fuel return lines to the engine compartment. The vent line goes to the carbon canister. Also new for 1970 is a NON vented gas cap. Sounds like your car has been altered if you cannot find the vent tube from the tank or the hard line going to the canister up in the engine compartment. Did you replace & install a 1969 and older sending unit instead of the 1970+ type? 1970 and newer cars were Federally mandated to have this.