Wanted: The perfect startup for a TSIO-360

[N231BN]

Thanks for sharing your experience.
My research and experience is a little different than yours.  Quote from "Continuous Flow Fuel Injection Systems," Aircraft Maintenance Technology, November 1998:
"All TCM pumps rely on a “by-pass valve”
which serves to purge vapors from the lines
when the boost pump is engaged prior to
engine start up."
This article reviews fuel setup on the various variants of TCM engines from naturally aspirated through fuel injected.  It also has an interesting side bar about the complexity of setting up a TSIO-360 with aftermarket intercoolers and the Merlin wastegate controller.
If you are seeing excessive fuel being dumped when running the boost pump while at ICO on your mixture, something is not correct.  I would be worried that there is some damage/scoring/seals allowing leakage or you are not adjusted to get full cut-off.  I run the boost pump frequently for cold and hot starts and have never observed excess fuel during this process.  I looked at my setup in an -LB engine and there is a vapor line returning to the tanks from the top of the fuel pump.
SID97-3G also has coverage of the full range of pumps.  All these pumps also show a vapor return line.
Just sharing my experience and research.  Use your own judgement and make your decisions about safe operation.
But, always good advice to be aware to look for fuel leakage.  If you are going to try the boost pump operations it would be good practice to try this where you can make a good inspection for any excess fuel in and around the engine.  It is definitely not a good idea to have lots of excess fuel pooling and try to start an engine.
Good luck and be safe.

Normally you would be correct, however the lastest version of the TSIO-360 fuel pump has a different mixture control assembly that does let fuel pass from the electric pump when in ICO. I had my pump rebuilt(exchange) a couple years ago and talked to the fuel shop about it. If you send in an older pump you won't get full core credit because the mixture assembly is obsolete.