Non starter.I read the threads about the fuel pumps/filters and am a bit lost.(

I am e retired old school mechanic,and this new stuff is a pain in the bum,with all these needless sensors.)I have checked LP fuel flow to pump,but read somewhere it needs to be 50psi or it won't prime the HP pump.Is this so?I know you shouldn't,because in good condition THERE IS 5000 PSI AT CRANKING there, but I cracked the feed line to the rail,and cranked the engine to see if fuel was flowing.I had a few air bubbles and a dribble of fuel.Taking things in sequence,is there a rule of thumb way to test LP pump pressure,eg blasts into container or just flows on exit from main filter housing?.Where is the HP pump micro filter?I have not yet checked the solenoid seal ,but heard it clicking .How much effect do sensors/ wiring plugs have to cause these symptoms?You young whizz kids must know, thanks in advance for any gen.