Fuel expansion tank

[TOADFOOT (john newton)]

what is the purpose of the fuel expansion tank

[Ole-XKE1974 (Ole Würtz)]

I believe in a closed tank and fuel delivery system, it’s for those times where temperature causes the air (and fuel) to expand and the tank becomes pressurized. It expands into the expansion tank.
I could off course be wrong.
Cheers … Ole

[John_Walker (69 FHC. . . $ via PayPal)]

@Ole-XKE1974

I believe in a closed tank and fuel delivery system, it’s for those times where temperature causes the air (and fuel) to expand and the tank becomes pressurized. It expands into the expansion tank.

I could off course be wrong.

That’s my understanding as well. Earlier cars had a vented fuel cap so the tank “breathed” depending on the temperature. This allowed rawt hydrocarbons, fuel vapor to be released adding to pollution. In a closed system the fuel cap is not vented to the atmosphere so the ranks breathes into the expansion tank.

[MartinScherz]

My tank vents to the trunk. So the expansion tank is then obsolete?

[saabguy (Lester)]

See explanation under “Would this be over the top” thread, about half way down. Would this be considered “Over the Top?”