Gas Tank Issue

[Tkrysl]

Evening,

Today after filling up for the first time, I smelled gas driving home. After investigation, it is coming from what looks to be some sort of breather return on the sending unit.

Is there a cap that belongs on this open port? It's a terrible picture but the shiny piece circled with yellow has an open end.

Appreciate your willingness to give this noob some knowledge.

[billthompson]

if memory serves one of those is a vent line that goes to a folded piece of tubing assembly that runs up in the space of the cab at the passenger side of the tank, directly behind the passenger door latch. seems like the fuel line exits the cab in the floor over there too. dont qoute me cause its been years since i messed with a tank in a pickup cab. if you dont find anything over there let me know and ill dig though the books when i get to the shop

[billthompson]

i looked at lmc catalog and think that line may be the one that goes up to the carcoal canester. either way its a vent line and needs to be plumbed outside the vehicle
or capped off or youll always have fumes

[ncpetersc]

I think the tubes circled in red are go to that vent tube up the passenger side of the cab.

The "uncapped" tube is usually connected to another fuel line coming back from the fuel pump.

Maybe you have a fuel pump with out this connection (2 lines vs. 3 lines)?

Also, I cannot tell if there is a hose connected between the neck and the tank on the drivers side?

[cerial]

You have a 71/72 eec tank. The picture below is how I am running my lines. You plug that sending unit line. Running the lines as above will avoid fuel entering the vent line if on your side/roof.

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[jbarron]

The port on the sending unit is for a return line from the fuel pump.
If you do not have a fuel pump with a return then block it off.

[ncpetersc]

There were different tanks and fuel setups. I think the tank you have is referred to as "with EEC" which is some sort of emissions control and is associated with having the charcoal canister in the engine bay.

There are different sending units as well. Some only have the fuel supply line, some have two connections like the one you (and I) have. It's sometimes referred to as a 'return' line, but I have been told it also serves more of a venting purpose, but it would connect to a separate fuel line running all the way back to the fuel pump.

Another note. If you do have an "EEC" system, it's vented through the charcoal canister and thus would use a "sealed" gas cap. The non EEC types use a "vented" gas cap.