[Richard L]

So far this is the only time I have encountered the fuel injectora re not powered up (only 5 seconds) at the pre-crank position.

We insisted on the system will only turn on when there is 12V present at the fuel injector. This will avoid any accidental/pre-mature spray when the engine is not running.

At the post crank postion, I suspect the same reason, if the engine is not running, the ECU switches off the (+) supply to fuel pump and injectors.