details...
I used a cheap little valve pulled from amazon that you can get in several NPT sizes and coil choices.
http://www.amazon.com/gp/product/B00827FP26/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A3A3DZ03XONGGK
With a -6 fitting in from the pump and a -4 out to the two injectors. The body of the solenoid is supported with a -26 adel clamp and -12 to the engine mount.
Power is tied to the pump.
I have around 6-8 feet of 3/8 hose from the pump located on the tank in the baggage area to the firewall... a few inches of 3/8 tube to the valve in the engine compartment... a short run from there with 1/4 tube to a tee then ss flex -4 line to the injectors.
Check valves are rated at opening pressure and don't necessarily close at the same pressure... they reliably prevent reverse flow, and once seated, will only open with pressure that is close to the rated value. Consider that a typical small in-line check valve with .5 psi open pressure only requires about 2 feet of head to open... with a couple of gees, less than a foot is needed. Most any tube routing will end up with some available head to work pressure the valve open in bumps and throw a brief puff out of the system in addition to the slow and fuzzy closure process.
Recently, we flew a 6-ship air show formation routine with 4 smoking that included much practice and filming that highlighted the poor cut off for everyone... 3 with check valves of and one without. They all looked the same at smoke off with lots of trailing and dribbling smoke and included numerous bump / gee induced puffs and spits well after smoke off.
There may be other ways to get clean cut off... I am very pleased with how this is working though. Hopefully the valve will withstand the heat and give good service life. I have it located in a relatively cool area and have a spare
I will report back if it fails.
Running a small power wire back to the pump is pretty simple for testing but does require quite a bit of effort for the final run to tuck it away with others in a common run... only time though, and hey it's fun
Here is a photo: