1992 Ford F-250

I have replaced every sensor and the coil and pickup coil because the truck would not restart after it warmed up now I have found that there is fuel in the cylinders after you shut it off causing the spark plugs to foul. After it sits a while it will start again. Could there be a wiring short causing the injectors to open after the ignition is shut off letting fuel dump into the engine? All plugs are fouled not just one or two. Could it be a bad injector circuit in the computer. Ok now I have replaced the fuel regulator and the truck still runs badly. If you pull the fuel pump fuse out it runs fine until the fuel pressure drops but it might run 15 seconds before it dies. Once it warms up it will not restart but if you pull the fuel pump fuse it will start back up. Could a plugged fuel return line cause excess fuel to the injectors?