fuel tank sending unit
 

my friend has a 72 chev custom 10, we can't figure out why there is an extra line coming out of the sending unit in the fuel tank, it runs up the back of the cab into the roof somewhere, is this a vent or something? why does it go up into the roof? It apears to be factory

I believe it is a vent they started using in 71'.

You will see the double vent on AC equipped trucks for the most
part. Does your friends truck have AC?

Jim

no this truck does not have a/c, it is about the plainest truck you'll ever see. it is all original he bought it from the original owner, so it is the original fuel tank for the truck.

Does the smaller line go to the evaporative canister or to the fuel pump (with the larger line)?

Jim

The vent line that goes up into the corner of the cab was part of the EEC (Evaporative Emissions Control) system. This vent line was produced starting in 1971 and continued into 1972 and was equipped on all 1/2 ton trucks and also on a few 3/4 ton trucks. The in-cab gas tanks in 1971 and 1972 on all 1/2 ton and some 3/4 ton trucks had the "new" style gas tank with the breather hose going from the top of the tank to the filler neck.