[Kenth]

Originally Posted by SRR

Are you positive your gas cap is venting?

LeMans gas caps are supposed to be closed and venting thru a vent line from the filler tube.

[Kenth]

I have found fuel "drain-back" thru fuel inlet is a myth.
Fuel evaporation is not, as the carb is 100% vented to atmosphere.
It was always the case then and more so now with todays fuels aimed for closed fuel systems and fuel injection engines.

FWIW

[DANTIP]

Originally Posted by Kenth

I have found fuel "drain-back" thru fuel inlet is a myth.
Fuel evaporation is not, as the carb is 100% vented to atmosphere.
It was always the case then and more so now with todays fuels aimed for closed fuel systems and fuel injection engines.

FWIW

So, when enough fuel evaporates or leaks from the float bowl, the needle valves open and some fuel may come in until the fuel pressure goes down. Then it seems like fuel would continue to evaporate potentially all the way to the fuel pump??

Then when we go to start the engine, fuel has to fill the fuel line and the float bowl(s) before the engine can start? I’m not sure how cars with the return line would act differently? Are there other considerations I’m missing?

[grivera]

Originally Posted by Kenth

LeMans gas caps are supposed to be closed and venting thru a vent line from the filler tube.

This is how my line is connected - from filler neck to fitting- no line on the other nipple and no idea wher it would lead to/connect

[Kenth]

Originally Posted by grivera

This is how my line is connected - from filler neck to fitting- no line on the other nipple and no idea wher it would lead to/connect

Here is a pic from the 1969 Service Manual:

[Shiny]

Originally Posted by grivera

This is how my line is connected - from filler neck to fitting- no line on the other nipple and no idea wher it would lead to/connect

Originally Posted by Kenth

Here is a pic from the 1969 Service Manual:

Similar design on my 70 LeMans.

grivera has the U-shaped pipe in place and the diagrams show nothing connected to the open end of the pipe, like his. Assuming the grommet is out of place intentionally, that's the vent design and it should work as intended.

Why they used the u-shape pipe, I don't know. Probably something to do with managing liquid gas... maybe regulatory? Seems weird because, at least on mine, the tank has another vent on the front side that is basically a vertical tube. It has a filter stuffed in it, but no u-shaped turn. ????

Mike