Hi everyone, I'm a new F150 owner and I've a question I was hoping someone could clear up for me.

I've got an 89 F150 XL Lariat.
There seems to be a wiring issue with the fuel pump wiring circuit.

Running direct power(bridging the relay to the fuel pump output-yellow to brown) works fine and the truck will run.
The relay has been replaced.

Constant power on the yellow wire to the relay is good as indicated above.

12V from the EEC relay on the red wire is good when key forward.

12V Output to the brown wire(fuel pump) is good when nothing is connected to it, and key forward. When I connect the fuel pump, that voltage drops out.

The inertia switch is being bypassed.

When I test the ground(tan/lt grn) wire with the key off, it is fully grounded. When the key is turned forward, it drops to around 6V.

Is this indicative of an issue with the PCM? And if so, is it ok to use a normal switching relay instead of the fuel pump relay to just supply power to the fuel pump at key on, and make sure I don't let the key sit forward without cranking? Or will that configuration cause other problems?