Fuel pressure regulator on return line setup

[Ralph Inkster]

Sorry for appearing dramatic, but I find this thread to be truly SCARY!

I too am in league with earlier posters who advise to "DON'T DO IT." But I will go a bit further to suggest what you should do.
You should contact the fuel injector manufacturer technical support and describe what you are experiencing (or trying to prevent experiencing), describe your non-standard fuel plumbing set-up, and follow their suggestions. Also talk through what is, and how to prevent 'vapor lock' with them.
I did a quick web search and found that at least one manufacturer offers a purge valve set-up that mounts on top of the engine to clear vapor lock from the fuel spyder, you might institute this type of solution for hot starts.
In the mean time, if you go flying CLOSE THAT VALVE!

As Scott said:
"Be very careful when designing / modifying the fuel system for an aircraft.

Fuel system issues is one of the highest causes of engine stoppage in experimental aircraft.

[amerkarim]

Thanks All,

Makes more sense to me now.

Where I fly it is hard to get decent avgas and it is very expensive when you get it, so a lot of flying will be with mogas that is easily available and cheap (Shell V Power 98 RON), outside air temps can also get to 40 degrees centigrade, hence my apprehension about vapour lock and installing a return line to start with.

I like Mark's suggestion of a reducer sitting in my AN6 return line with a 1/8" orifice to allow just enough flow to get bubbles and vapour out. I also have a non return valve that I will fit just before the return line plumbing to stop air coming back the other way. Let me have a go and see what happens.

Many thanks again and happy landings

Best

Amer