Ford Repair: No Fuel Pressure, fuel pump relay, ford 460

Question
I have a 1991 Silver Eagle motor home with a Ford 460 Fuel Injected engine and C-6 transmission on a Oshkosh chassis. I started the engine Last Friday and the engine started fine but died as soon as I depressed the gas pedal. It re-started after turning over a few times and again died when the gas pedal was moved. That was the last time it started. I checked the fuel pressue at the injectors and had none.The pump did not start when the key was turned on. Installed new pump and same problem. Checked voltage to pump and it only has 4 volts to the pump and 8 volts to the sending unit. Shouldn't the pump have 12 volts as soon as the key is turned on to build pressure to start.The pump is not Ford but Oshkosh. Any suggestions as to what failed to cause the low voltage to the pump would be greatly appreciated. I hooked the old pump directly to a battery and it ran. Plugged it into the wiring harness out of the tank and nothing.Reason I guess is the low voltage. Thanks Pat  

Answer
Hello and thanks for the question...I'll try to help.
 You are corret in the assumption that low voltage will cause a low pressure furl pump condition.
Your vehicle should be fitted with a fuel shut off switch, the location should be in your owner's manual.
 Remove the wire plug and check for voltage there....it should be 12v. If it's not, locate the fuel pump relay, and check for voltage there, 12v again should be present. On the shut off switch, make sure it's set. It is meant to kill the fuel pump if you're in an accident by openning the circuit and shutting power off to the fuel pump. Also, check the wires going from the fuel pump that run along the underside of the vehilce. Make sure they have not been torn, melted, corroded, pulled apart.
Hope this help,
Erik