Extra fuel tank line?

[pdallas]

My 1984 310 has a 40 gal fuel tank. For some reason it has 4 fuel lines: one to fuel pump, one return, one to generator, and one that is just there. I discovered the fourth line when I filled the tank to capacity, it overflowed onto the ground. Not the most pleasant thing to occur at a fuel stop. Does anyone have any idea what's was the intended use for the extra line. Can I simply plug the line?

[Smartstream]

Originally Posted by pdallas

My 1984 310 has a 40 gal fuel tank. For some reason it has 4 fuel lines: one to fuel pump, one return, one to generator, and one that is just there. I discovered the fourth line when I filled the tank to capacity, it overflowed onto the ground. Not the most pleasant thing to occur at a fuel stop. Does anyone have any idea what's was the intended use for the extra line. Can I simply plug the line?

I can't speak for sure about your tank but on mine which is 60 gal and a diesel there are several spare ports on top of the tank. I guess they put extras in for more than one application.

I too found the existence of an open port the first time I filled the tank. I dropped the tank and there are two ports with pick up tubes and several return/vent ports. One unused port had a 90 degree elbow and no plug. I don't recall how the vent was set up, fading memory, but I brazed an elbow in the filler tube near the top and ran a hose from the open elbow. I thought it might help vent some air and foam during fill up.

Cheers, Dan

[Wsmith]

I think it is a vent line. My in bed 98 gallon diesel tank has a vent ell reducer down to 1/8" and a few more penetrations that are plugged on the top then it has the gravity feed fitting on the bottom that feeds into the neck of the truck fill tube.

[ROBERTSUNRUS]

Hi, possibly for a carbon canister that someone disconnected or removed?

[AirRowan]

Mine (345 80gal) had one line that led to a carbon canister on the pass side of the raidiator. I think it is both a vent and a return from the carbon canistor.