I have a 1993 e-150 with a 4.9L six (300ci) fuel injected, (with an individual injector on each cylinder).
I have one cylinder that keeps filling with fuel (#5 cyl.)
I have tried replacing the one injector on that cylinder, did not help,
doesn't matter if the injector wiring is hooked up or not, as soon as I turn the key on and pressurize the fuel rail, and crank the engine over, that one cylinder starts squirting out a massive amount of raw fuel. (Compression is OK across all the cylinders.)

Has anyone have an idea of what is happening in this system, someone I know says that the fuel pressure regularator needs to be replaced, but I wonder why only one cylinder fills up with fuel?

 

If the injector is unplugged, it should spray no fuel regardless. Have you checked actual fuel pressure? It should be between 30 and 40psi.

 

Haven't tested the fuel pressure yet, that is my next step, I need to locate a fuel pressure gauge, (I might be able to get a loaner from my local Auto-Zone, as I know the do loan some tools)