I need some help, my fuel pressure dies the moment I turn off the engine, it is running rough as, huge lag under acceleration, blowing black smoke....

Here's what I've done so far, obviously I have a leak somewhere...... Injectors out and hydro bath cleaned and tested..... New rising rate fuel pressure regulator installed..... put in a secondary one way check valve before the fuel rail to stop fuel pressure bleed back to pump, so by process of elimination I've only got the fuel pump left to swap out right???

What I don't understand though is..... I have a check valve on the outlet from the fuel tank before it gets to the fuel rail....... the injectors are supposedly good and there's a new fuel pressure regulator on the return side of the fuel rail.... so theoretically the system should hold pressure once I turn off the key, even if the pump is faulty..... but it plummets once the key is turned off....


WHAT AM I MISSING PLEASE?????

 

if it’s pissing black smoke and pressure drops off at the turn of the key I’d think you have an injector stuck open.

are you running OEM injectors?

can you swap a set in and see how it does?

 

I had the injectors out and sent for ultra sonic bath and flow tested, guy at shop said they where fine, that was my original thought too... they are Deuschwork 650cc's....
I wonder though if his testing only tested flow and not stop/start???