bought this to fix fuel drain back problem

I've used one of these on my old mechanically injected Cummins for years with great success. That engine is particularly problematic in this regard because once air gets in the lines you have to manually bleed the injectors, which is rather a large PITA. Even the tiniest imperfection somewhere in the fuel system seems to be enough of an issue to cause bleed back without showing a leak or any other abnormalities except the resultant inability to start due to air getting in the injection lines.

I am putting one on the Mopar now too. I can confirm the symptom and behavior as described. You would think that technically this drainback is not possible, but it is. I was looking at the clear glass filter I have installed in the fuel line just the other day and it was dry after sitting for about a week. I cannot imagine how it could be evaporating three feet back into the line from the carb.