Fuel return line for carb motor?

[gasman]

Many years back Van published a service bulliten in his newsletter about installing a return line from the carb inlet to the tank that was valved so you could cycle some fuel to cool it off if there was a hint of vapor lock happening?

My question is .......... does anyone have this installed on their plane, and have they ever had to use it?

Thanks for your response.

 

[rocketbob]

As someone who has a lot of experience running 87 mogas in an RV I think a return line would be a good thing and I would go a step further and put a purge valve on the bowl drain to purge the carb for a hot start just like an AFP purge valve works for fuel injected engines.

 

[Rick_A]

Yes, I have one

I installed a return line for my O-360. I use a primer solenoid as the control valve.

My fuel pump switch is an OFF-ON-MOM, with the MOM for the purge valve. I can tell a big difference in the fuel pressure and speed of the aux pump when I used the purge. It really helps when the fuel has been subjected to a long period of a heat soak. A few seconds on the purge and the fuel pressure comes up fast and the pumps slows way down.

 

[Walt]

I had a purge valve on my carb and now have one on my AFP injection, if you live in a hot climate then its a REALLY good idea IMO.

 

[krw5927]

This is an intriguing idea that I haven't heard about before. One question: where does the return line go to? Do you need a double valve with provisions for a return line and plumbing back to each tank, or can you just run it back to a tee immediately downstream of the standard valve?

 

[frankh]

I have the AFP dump valve..Hot starts are almost as easy as cold starts.

Frank

 

[Walt]

This is an intriguing idea that I haven't heard about before. One question: where does the return line go to? Do you need a double valve with provisions for a return line and plumbing back to each tank, or can you just run it back to a tee immediately downstream of the standard valve?

I plumbed a line back to one tank during the build, no fancy valve needed and no special procedures required for purging.

An alternate method would be to plumb it in before the fuel selector, then select the opposite tank during purge, this would force the fuel back to the tank ranther than merely recirculating the hot fuel.

 

[rocketbob]

Today I made a short trip to pick my mother up so she could visit the grand kids. Any time mom flies, I have to be on my game. The slightest abberations make her nervous. I am flying a friend's RV-6 and it has a bit of a goofy fuel system and a gascolator. Stopped for gas and after a quick turnaround, it started vapor locking on me. On 100% 100LL since due to the goofy fuel line routing I recommended we don't fly it in hot weather on mogas. A purge line and vapor bypass would have sure been welcome today.