By the way the EEC Computer has nothing to do with voltage at the EEC or Fuel pump relays. It can only ground one side of the coil of the fuel pump relay on the EEC IV, FI, OBD I system.

Also you say this is a 1989 motorhome, most (90%) of 1989 motor homes were 1988 E350 Ford incomplete chassis. I though that the 1988 E350 460 was still Carb and not FI. If so you will still have a fuel pump and other relays that make when you turn on the key but you would have a Check Engine Light (MIL).

You did not say how you did a stand alone test of the fuel pump relay.