Did you change solenoid itself? It was cheap I think, i remember supplying solenoid directly from the batteries to exclude any harness problems
Mark are you resolve your problem? I see this post was along time ago but I’m searching of answers I have the same problem
I remember changing engine harness, fuel shut off valve/solenoid and later ECM because I was getting intermittent misfire on low RPM, also had damaged ECU because of solenoid valve was taking too much current to open, solenoid valve is supplied through ECM, and it can burn your ECM very easily, it smells burnt electronics really bad and your truck will not start of course throwing error codes, had to make delivery so I put hot wire on solenoid and truck runt like nothing happened except red and yellow lights on dash, sent ECU for repair and they said there was too much damage to be fixed :/