Fuel Vapor Separator

[Beekeeper1970]

I have a 69 Coronet and I know some of these cars came with fuel separators with a return line and others did not. I’m trying to learn more about how these work and if they could help in any way preventing fuel from leaking out the vent lines.

I have a new tank, new non vented cap and new vent lines which I have verified are routed correctly and not inadvertently swapped. As far as I can tell, everything is correct just as it should be. When the tank is completely full, it eventually pushes fuel out the vent lines onto the ground. Not immediately but instead once the car is nice and warm after driving a bit. This makes me think expansion.

Could adding a vapor return line and fuel vapor separator help? Not sure if the separator on the engine pulls vapors from the tank or only sends vapor and fuel back to the tank.

 

[bearman]

Do you have a vapor line at the neck and does the fuel cap block it off when you tighten it down. Just a thought

 

[Beekeeper1970]

Do you have a vapor line at the neck and does the fuel cap block it off when you tighten it down. Just a thought

no vapor line at the fill neck. Should there be one?

 

[dadsbee]

Return line has ZERO to do with tank venting. I'd suspect your lines are hooked up backwards, long vent line that runs back to the filler neck is the one that connects to the shock tower tube and the short tube at the front of the tank connects to the vent up into the trunk.

 

[Beekeeper1970]

Return line has ZERO to do with tank venting. I'd suspect your lines are hooked up backwards, long vent line that runs back to the filler neck is the one that connects to the shock tower tube and the short tube at the front of the tank connects to the vent up into the trunk.

Good to know that the fuel separator and return line won’t have any effect.

I think I have the connections correct but I’ll double check once I drive some of the gas out and can shine a light down the filler neck.

 

[Sixpactogo]

Fuel separator and return line were installed on Hemi & some 440 cars simply to avoid vapor lock that was prevalent. It sounds like you are building pressure in the tank and your venting is not working as it should. The 1/4" tube near the top of your filler tube should be hooked to the tubing that goes up into the frame rail. I bet it is plugged. If you can't get that fixed, I would use a vented cap.