Fuel Return Line... Why?

[DaveandMarion]

Hi All,

I'm not sure what it's for (for a single solex 34 pict 5 1.9 petrol set up).

Google says it may be down to keeping the fuel lines compatible for EFI - that's about as much as I can figure out, but then the carb is built for having a return line anyway.

My other theory is that the the fuel goes in one end, is used by the carb and then returned to the tank. If i'm right on this then it means VW created a perpetual motion engine years ago, and all this fuss about fossil fuels runninng out has been a total waste of time. However, it doesn't explain my rubbish MPG - so I might be wrong on this.

So, back to my original question - what's the benefit of having a return line for this type of carb?

Cheers!

[sarran1955]

Hello,

Designed for fuel injection ring main set up.

Keep it, (though I think the perpetual motion theory may be flawed )

Make sure the rubber hoses and fuel filter are in good condition.

Cordialement,

[DaveandMarion]

Thanks for clearing that up!

It was when I was replacing the pipes I noticed it. Given the return line is connected to this carb, do you know if it actually returns anything?

Cheers,

Dave

[Footprint]

Not sure about your carb, but many vehicles have a pump that runs constantly and a spring loaded release valve that vents excess pressure back to the tank.

[bigherb]

A couple of reasons. As the pump supplies more fuel than the engine ever needs returning the excess back to the tank uses less power to drive the pump more importantly petrol boils a relatively low temperature forming vapour bubbles in the fuel line, the return line allows the bubbles an easy path back to the tank.