Fuel Return Valve Redux

[paulyg]

Hey All,

 

I have been combing through old posts to ascertain the value (or devalue) of having a fuel return valve with a carb setup. I recently plugged the mummified hose dangling off the return hardline to hopefully reduce the gas smell in my engine compartment, but some previous discussions have me wondering:

 

1) Is it worth having a return valve with a carb setup (Weber 32/36)

and...

2) What is the part number for the valve and how is it installed?

 

Please inform... I suspect that a fuel system refresh is in my future, even though I've already done the engine bay rubber. 

[stephers]

No remove it for the weber, just run a hose from the pump to the carb   less stuff to leak     It was used with the solex to return fuel back to the tank on cruise when under high vacuum in the intake, engineers figured that carb didn't need as much fuel when cruising      plug the vacuum pick ups with a little cap that you can pick up at any auto store

 

Thanks, Rick

[TobyB]

I mildly disagree-

I've had mechanical pumps wear out needles and seats in the Webers.

 

If I was bored, and working on it anyways, I'd play with using the return

to bleed back a small amount of fuel, or just fit the Jeep filter that Tom uses.

Maybe with a restrictor in the return line, as I've had other experiences with

open return lines and SU's

 

The Weber's a priss about pressure, so doing things to even it out/ regulate

it always helps drivability and maintenance.

 

You kids are too young to remember 'vapor lock,'  

but deadheaded systems always have that potential, and starting in the late

60's, carbed cars started to have systems to alleviate it.  They usually involved

some sort of modulated return.

 

Things go full circle, of course, so by about 2000 BMW stopped using return

systems for EFI, and went back to deadheading, as they were discovering

that the return heated the fuel too much in hot climates...  and caused EPA

problems.

 

t

life is better electric.  So someone give me a Model S, huh?

[John76]

I'm with Toby ... but I disagree a bit more than "mildly".

A fuel return system really helps reduce vapor lock on a carb-equipped car by keeping the fuel cool and not deadheading against the float needle.

Use the stock BMW return valve if you have it. It has a variable return that is regulated by manifold vacuum.

Or install a Jeep filter that has a fixed orifice return line. Check the specs for the orifice diameter... .040, .050, or .060", and pick one that gives you the desired fuel pressure to the Weber.

 

[tech71]

17 hours ago, paulyg said:

how is it installed?

Best pic possible without removing my air cleaner. It mounts to intake manifold on a small bracket with a single 6mm bolt.

Mine works reliably so I just leave it alone however,  both 1976 cars I own developed a rust induced leak in the metal return line where its stuffed up next to the pedal box, causing seepage and fuel smell.

Had to replace a section of the line, something to bear in mind.

Instead of just capping the return line in engine compartment I suggest you cap the return fitting on your fuel tank.

Edited October 21, 2022 by tech71

[paulyg]

3 hours ago, John76 said:

I'm with Toby ... but I disagree a bit more than "mildly".

A fuel return system really helps reduce vapor lock on a carb-equipped car by keeping the fuel cool and not deadheading against the float needle.

Use the stock BMW return valve if you have it. It has a variable return that is regulated by manifold vacuum.

Or install a Jeep filter that has a fixed orifice return line. Check the specs for the orifice diameter... .040, .050, or .060", and pick one that gives you the desired fuel pressure to the Weber.

 

You got a part number or listing for that OEM return valve?

[2002iii]

16 minutes ago, paulyg said:

You got a part number or listing for that OEM return valve?

13311259194