There is a fuel cut off solenoid in the injection pump that has to be wired to a switched 12v source. When there's no power going to the solenoid (ign off) then it stops fuel flow. Sounds like you have it hooked to constant 12v instead of switched. I can't remember off the top of my head which wire it is, but it is one of the larger gauge wires in the injector pump harness. I will check the wire color for you next time I go out to my truck.

85 4x4 Pickup, 267K, 4d55 Conversion, Sway-A-Ways, Dual Batteries