Fuel coming out of the return line from carbs?

[70z4fun]

Working on my car today, and I left the return line off where the hard line hose goes into the rubber hose by the fuel filter.

Started the car, and a steady stream of fuel came out. Is that normal? I always thought that was an air vapor line?  I did not realize that the hose going from the hardline hose that is the return line down on the frame rail had any pressure?
 

I don't even remember checking to see if those clamps were tight.......

 

IF that is not normal, I could use some advice..........

 

 

[siteunseen]

I think  the over flow after the bowls are full go back to the tank through that teturn line it's a open flow circuit. It has to go somewhere.

The efi cars are even more at 32psi constant fuel ptessure. Our SUs are 3.2 psi.

[SteveJ]

23 minutes ago, 70z4fun said:

Working on my car today, and I left the return line off where the hard line hose goes into the rubber hose by the fuel filter.

Started the car, and a steady stream of fuel came out. Is that normal? I always thought that was an air vapor line?  I did not realize that the hose going from the hardline hose that is the return line down on the frame rail had any pressure?
 

I don't even remember checking to see if those clamps were tight.......

 

IF that is not normal, I could use some advice..........

 

 

Yes, that is normal. It is a return line, not a fuel vapor line. The vapor line is routed differently and ends down below the ballast resistor/coil area. 

As @siteunseenwas saying, when the floats rise in the float bowls, they cut off fuel from going into the float bowls. Since this is a low pressure system that is not dead-headed, the fuel must go somewhere.

The block on the right end of the fuel rail is where you go from supply to return.

[70z4fun]

Ok, I feel better 😉
I thought something weird was going on. I know the three way valve on the air filter side is air vent, but for some reason I thought the fuel rail was an air vent too.

I noticed that the end has a smaller hole, so it was "squirting" out fuel......

It makes sense that the gas needs to go somewhere...... I will replace that line and make sure that the hose clamps are tight.

 

Thanks

Bob

 

 

[SteveJ]

That orifice is the "fuel pressure regulator". That is what allows the pressure to stay around 3 to 4 PSI on the fuel rail.

[siteunseen]

46 minutes ago, 70z4fun said:

I noticed that the end has a smaller hole, so it was "squirting" out fuel......

That's the first iteration that I've seen of a fuel pressure regulator for the Zs, smaller hole on the return line back to the tank. I guess it keeps the bowls full without overflow. More in while running then excess goes back without overfilling the bowls..

I'm sure it was done before but my 1st experience with the larger in vs. the smaller outlet.

 

 

Edited March 13, 2022 by siteunseen