willie_wonka
+1y
If the truck has the stock motor with the stock rails, then originally the fuel pump was controlled by a module that varied voltage to the pump to regulate fuel pressure. If the engine is still stock and controlled by the original ECM then there is a sensor on the rail that tells the ECM what rail pressure is so it can control the pump accordingly. If you want it work worth a shit at all, you should probably get a stock pump in the fuel cell. The ECM (assuming you are still using everything else stock but the tank and pump) is not going to like not seeing a pump or any changes in rail pressure when it commands it. At the very least, you will get a service engine light and probably poor driveability. You say it was running with the return system. I am willing to bet thats what you were told and not what you saw because then the stuff would already be installed correctly. I don't doubt that the truck did run with the external pump and regulator but I am willing to bet it ran like shit. I am not trying to discourage you, alot of race cars(read mustangs) have been converted to return style systems but they also have been tuned by a dyno tuner to do so, either programming the fuel rail sensor and fuel pump driver module out of the equation or ignoring the SES light. When I first read the post I thought the truck had a V8 swap or something like that. I am not trying to sound like I know it all, I may be wrong, but I am a certified Ford lead tech and I have built a few mustangs as well.